CVE-2025-71088 (GCVE-0-2025-71088)

Vulnerability from cvelistv5 – Published: 2026-01-13 15:34 – Updated: 2026-02-09 08:34
VLAI?
Title
mptcp: fallback earlier on simult connection
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 01b7822700f2256900089e00390e119e1ad545df , < b5f46a08269265e2f5e87d855287d6d22de0a32b (git)
Affected: 1e777f39b4d75e599a3aac8e0f67d739474f198c , < c9bf315228287653522894df9d851e9b43db9516 (git)
Affected: 1e777f39b4d75e599a3aac8e0f67d739474f198c , < 79f80a7a47849ef1b3c25a0bedcc448b9cb551c1 (git)
Affected: 1e777f39b4d75e599a3aac8e0f67d739474f198c , < 25f1ae942c097b7ae4ce5c2b9c6fefb8e3672b86 (git)
Affected: 1e777f39b4d75e599a3aac8e0f67d739474f198c , < 71154bbe49423128c1c8577b6576de1ed6836830 (git)
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    Linux Linux Affected: 6.2
Unaffected: 0 , < 6.2 (semver)
Unaffected: 6.1.160 , ≤ 6.1.* (semver)
Unaffected: 6.6.120 , ≤ 6.6.* (semver)
Unaffected: 6.12.65 , ≤ 6.12.* (semver)
Unaffected: 6.18.4 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/mptcp/options.c",
            "net/mptcp/protocol.h",
            "net/mptcp/subflow.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/mptcp/options.c",
            "net/mptcp/protocol.h",
            "net/mptcp/subflow.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.2"
            },
            {
              "lessThan": "6.2",
              "status": "unaffected",
              "version": "0",
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              "status": "unaffected",
              "version": "6.1.160",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.120",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.65",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.19",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.160",
                  "versionStartIncluding": "6.1.110",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.120",
                  "versionStartIncluding": "6.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.65",
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                }
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              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-09T08:34:39.891Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/b5f46a08269265e2f5e87d855287d6d22de0a32b"
        },
        {
          "url": "https://git.kernel.org/stable/c/c9bf315228287653522894df9d851e9b43db9516"
        },
        {
          "url": "https://git.kernel.org/stable/c/79f80a7a47849ef1b3c25a0bedcc448b9cb551c1"
        },
        {
          "url": "https://git.kernel.org/stable/c/25f1ae942c097b7ae4ce5c2b9c6fefb8e3672b86"
        },
        {
          "url": "https://git.kernel.org/stable/c/71154bbe49423128c1c8577b6576de1ed6836830"
        }
      ],
      "title": "mptcp: fallback earlier on simult connection",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-71088",
    "datePublished": "2026-01-13T15:34:50.377Z",
    "dateReserved": "2026-01-13T15:30:19.649Z",
    "dateUpdated": "2026-02-09T08:34:39.891Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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