FKIE_CVE-2025-71088

Vulnerability from fkie_nvd - Published: 2026-01-13 16:16 - Updated: 2026-01-14 16:26
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: mptcp: fallback earlier on simult connection Syzkaller reports a simult-connect race leading to inconsistent fallback status: WARNING: CPU: 3 PID: 33 at net/mptcp/subflow.c:1515 subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1515 Modules linked in: CPU: 3 UID: 0 PID: 33 Comm: ksoftirqd/3 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1515 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 RSP: 0018:ffffc900006cf338 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888031acd100 RCX: ffffffff8b7f2abf RDX: ffff88801e6ea440 RSI: ffffffff8b7f2aca RDI: 0000000000000005 RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000007 R10: 0000000000000004 R11: 0000000000002c10 R12: ffff88802ba69900 R13: 1ffff920000d9e67 R14: ffff888046f81800 R15: 0000000000000004 FS: 0000000000000000(0000) GS:ffff8880d69bc000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000560fc0ca1670 CR3: 0000000032c3a000 CR4: 0000000000352ef0 Call Trace: <TASK> tcp_data_queue+0x13b0/0x4f90 net/ipv4/tcp_input.c:5197 tcp_rcv_state_process+0xfdf/0x4ec0 net/ipv4/tcp_input.c:6922 tcp_v6_do_rcv+0x492/0x1740 net/ipv6/tcp_ipv6.c:1672 tcp_v6_rcv+0x2976/0x41e0 net/ipv6/tcp_ipv6.c:1918 ip6_protocol_deliver_rcu+0x188/0x1520 net/ipv6/ip6_input.c:438 ip6_input_finish+0x1e4/0x4b0 net/ipv6/ip6_input.c:489 NF_HOOK include/linux/netfilter.h:318 [inline] NF_HOOK include/linux/netfilter.h:312 [inline] ip6_input+0x105/0x2f0 net/ipv6/ip6_input.c:500 dst_input include/net/dst.h:471 [inline] ip6_rcv_finish net/ipv6/ip6_input.c:79 [inline] NF_HOOK include/linux/netfilter.h:318 [inline] NF_HOOK include/linux/netfilter.h:312 [inline] ipv6_rcv+0x264/0x650 net/ipv6/ip6_input.c:311 __netif_receive_skb_one_core+0x12d/0x1e0 net/core/dev.c:5979 __netif_receive_skb+0x1d/0x160 net/core/dev.c:6092 process_backlog+0x442/0x15e0 net/core/dev.c:6444 __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7494 napi_poll net/core/dev.c:7557 [inline] net_rx_action+0xa9f/0xfe0 net/core/dev.c:7684 handle_softirqs+0x216/0x8e0 kernel/softirq.c:579 run_ksoftirqd kernel/softirq.c:968 [inline] run_ksoftirqd+0x3a/0x60 kernel/softirq.c:960 smpboot_thread_fn+0x3f7/0xae0 kernel/smpboot.c:160 kthread+0x3c2/0x780 kernel/kthread.c:463 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> The TCP subflow can process the simult-connect syn-ack packet after transitioning to TCP_FIN1 state, bypassing the MPTCP fallback check, as the sk_state_change() callback is not invoked for * -> FIN_WAIT1 transitions. That will move the msk socket to an inconsistent status and the next incoming data will hit the reported splat. Close the race moving the simult-fallback check at the earliest possible stage - that is at syn-ack generation time. About the fixes tags: [2] was supposed to also fix this issue introduced by [3]. [1] is required as a dependence: it was not explicitly marked as a fix, but it is one and it has already been backported before [3]. In other words, this commit should be backported up to [3], including [2] and [1] if that's not already there.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/25f1ae942c097b7ae4ce5c2b9c6fefb8e3672b86
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/71154bbe49423128c1c8577b6576de1ed6836830
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/79f80a7a47849ef1b3c25a0bedcc448b9cb551c1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b5f46a08269265e2f5e87d855287d6d22de0a32b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c9bf315228287653522894df9d851e9b43db9516
Impacted products
Vendor Product Version
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{
  "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 \u003c0f\u003e 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   \u003cTASK\u003e\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   \u003c/TASK\u003e\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 * -\u003e 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\u0027s not already there."
    }
  ],
  "id": "CVE-2025-71088",
  "lastModified": "2026-01-14T16:26:00.933",
  "metrics": {},
  "published": "2026-01-13T16:16:08.460",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/25f1ae942c097b7ae4ce5c2b9c6fefb8e3672b86"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/71154bbe49423128c1c8577b6576de1ed6836830"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/79f80a7a47849ef1b3c25a0bedcc448b9cb551c1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b5f46a08269265e2f5e87d855287d6d22de0a32b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c9bf315228287653522894df9d851e9b43db9516"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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