CVE-2025-71088

// CVE-2025-71088 PoC - MPTCP simult-connect race condition // This PoC demonstrates the race condition in MPTCP fallback handling #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/socket.h> #include <netinet/in.h> #include <netinet/tcp.h> #include <linux/mptcp.h> #define MPTCP_PATH_MANAGER 2 // Use in-kernel path manager void trigger_race_condition() { int sock_fd1, sock_fd2; struct mptcp_meta_info meta1, meta2; // Create two MPTCP sockets sock_fd1 = socket(AF_INET, SOCK_STREAM, IPPROTO_MPTCP); sock_fd2 = socket(AF_INET, SOCK_STREAM, IPPROTO_MPTCP); if (sock_fd1 < 0 || sock_fd2 < 0) { perror("socket creation failed"); return; } // Set MPTCP options to enable multipath int optval = MPTCP_PATH_MANAGER; setsockopt(sock_fd1, SOL_MPTCP, MPTCP_PATH_MANAGER, &optval, sizeof(optval)); setsockopt(sock_fd2, SOL_MPTCP, MPTCP_PATH_MANAGER, &optval, sizeof(optval)); // Note: This PoC requires specific kernel configuration and network setup // The actual race condition is triggered through specific TCP state transitions // that occur during simultaneous MPTCP connection establishment. // // Real exploitation requires: // 1. Two hosts establishing simultaneous MPTCP connections // 2. Specific timing to trigger the FIN_WAIT1 state transition // 3. SYN-ACK packet arriving after state change // // See kernel commit references for the actual fix: // - 25f1ae942c097b7ae4ce5c2b9c6fefb8e3672b86 // - 71154bbe49423128c1c8577b6576de1ed6836830 close(sock_fd1); close(sock_fd2); } int main() { printf("CVE-2025-71088 PoC - MPTCP simult-connect race\n"); printf("This vulnerability allows bypassing MPTCP fallback check\n"); printf("Through TCP_FIN_WAIT1 state transition race condition\n"); trigger_race_condition(); return 0; }

{"cve": {"id": "CVE-2025-71088", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-01-13T16:16:08.460", "lastModified": "2026-03-25T18:56:39.973", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fallback earlier on simult connection\n\nSyzkaller reports a simult-connect race leading to inconsistent fallback\nstatus:\n\n WARNING: CPU: 3 PID: 33 at net/mptcp/subflow.c:1515 subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1515\n Modules linked in:\n CPU: 3 UID: 0 PID: 33 Comm: ksoftirqd/3 Not tainted syzkaller #0 PREEMPT(full)\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014\n RIP: 0010:subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1515\n Code: 89 ee e8 78 61 3c f6 40 84 ed 75 21 e8 8e 66 3c f6 44 89 fe bf 07 00 00 00 e8 c1 61 3c f6 41 83 ff 07 74 09 e8 76 66 3c f6 90 <0f> 0b 90 e8 6d 66 3c f6 48 89 df e8 e5 ad ff ff 31 ff 89 c5 89 c6\n RSP: 0018:ffffc900006cf338 EFLAGS: 00010246\n RAX: 0000000000000000 RBX: ffff888031acd100 RCX: ffffffff8b7f2abf\n RDX: ffff88801e6ea440 RSI: ffffffff8b7f2aca RDI: 0000000000000005\n RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000007\n R10: 0000000000000004 R11: 0000000000002c10 R12: ffff88802ba69900\n R13: 1ffff920000d9e67 R14: ffff888046f81800 R15: 0000000000000004\n FS: 0000000000000000(0000) GS:ffff8880d69bc000(0000) knlGS:0000000000000000\n CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n CR2: 0000560fc0ca1670 CR3: 0000000032c3a000 CR4: 0000000000352ef0\n Call Trace:\n <TASK>\n tcp_data_queue+0x13b0/0x4f90 net/ipv4/tcp_input.c:5197\n tcp_rcv_state_process+0xfdf/0x4ec0 net/ipv4/tcp_input.c:6922\n tcp_v6_do_rcv+0x492/0x1740 net/ipv6/tcp_ipv6.c:1672\n tcp_v6_rcv+0x2976/0x41e0 net/ipv6/tcp_ipv6.c:1918\n ip6_protocol_deliver_rcu+0x188/0x1520 net/ipv6/ip6_input.c:438\n ip6_input_finish+0x1e4/0x4b0 net/ipv6/ip6_input.c:489\n NF_HOOK include/linux/netfilter.h:318 [inline]\n NF_HOOK include/linux/netfilter.h:312 [inline]\n ip6_input+0x105/0x2f0 net/ipv6/ip6_input.c:500\n dst_input include/net/dst.h:471 [inline]\n ip6_rcv_finish net/ipv6/ip6_input.c:79 [inline]\n NF_HOOK include/linux/netfilter.h:318 [inline]\n NF_HOOK include/linux/netfilter.h:312 [inline]\n ipv6_rcv+0x264/0x650 net/ipv6/ip6_input.c:311\n __netif_receive_skb_one_core+0x12d/0x1e0 net/core/dev.c:5979\n __netif_receive_skb+0x1d/0x160 net/core/dev.c:6092\n process_backlog+0x442/0x15e0 net/core/dev.c:6444\n __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7494\n napi_poll net/core/dev.c:7557 [inline]\n net_rx_action+0xa9f/0xfe0 net/core/dev.c:7684\n handle_softirqs+0x216/0x8e0 kernel/softirq.c:579\n run_ksoftirqd kernel/softirq.c:968 [inline]\n run_ksoftirqd+0x3a/0x60 kernel/softirq.c:960\n smpboot_thread_fn+0x3f7/0xae0 kernel/smpboot.c:160\n kthread+0x3c2/0x780 kernel/kthread.c:463\n ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245\n </TASK>\n\nThe TCP subflow can process the simult-connect syn-ack packet after\ntransitioning to TCP_FIN1 state, bypassing the MPTCP fallback check,\nas the sk_state_change() callback is not invoked for * -> FIN_WAIT1\ntransitions.\n\nThat will move the msk socket to an inconsistent status and the next\nincoming data will hit the reported splat.\n\nClose the race moving the simult-fallback check at the earliest possible\nstage - that is at syn-ack generation time.\n\nAbout the fixes tags: [2] was supposed to also fix this issue introduced\nby [3]. [1] is required as a dependence: it was not explicitly marked as\na fix, but it is one and it has already been backported before [3]. In\nother words, this commit should be backported up to [3], including [2]\nand [1] if that's not already there."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nmptcp: retroceso más temprano en conexión simultánea\n\nSyzkaller informa una condición de carrera de conexión simultánea que lleva a un estado de retroceso inconsistente:\n\n WARNING: CPU: 3 PID: 33 at net/mptcp/subflow.c:1515 subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1515\n Modules linked in:\n CPU: 3 UID: 0 PID: 33 Comm: ksoftirqd/3 Not tainted syzkaller #0 PREEMPT(full)\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014\n RIP: 0010:subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1515\n Code: 89 ee e8 78 61 3c f6 40 84 ed 75 21 e8 8e 66 3c f6 44 89 fe bf 07 00 00 00 e8 c1 61 3c f6 41 83 ff 07 74 09 e8 76 66 3c f6 90 &lt;0f&gt; 0b 90 e8 6d 66 3c f6 48 89 df e8 e5 ad ff ff 31 ff 89 c5 89 c6\n RSP: 0018:ffffc900006cf338 EFLAGS: 00010246\n RAX: 0000000000000000 RBX: ffff888031acd100 RCX: ffffffff8b7f2abf\n RDX: ffff88801e6ea440 RSI: ffffffff8b7f2aca RDI: 0000000000000005\n RBP: 0000 ... (truncated)