CVE-2025-71088 - Vulnerability Details

Vendors	Products
Linux Subscribe	Linux Kernel Subscribe

Link	Providers
https://git.kernel.org/stable/c/25f1ae942c097b7ae4ce5c2b9c6fefb8e3672b86
https://git.kernel.org/stable/c/71154bbe49423128c1c8577b6576de1ed6836830
https://git.kernel.org/stable/c/79f80a7a47849ef1b3c25a0bedcc448b9cb551c1
https://git.kernel.org/stable/c/b5f46a08269265e2f5e87d855287d6d22de0a32b
https://git.kernel.org/stable/c/c9bf315228287653522894df9d851e9b43db9516

Type	Values Removed	Values Added
Description		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.
Title		mptcp: fallback earlier on simult connection
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/25f1ae942c097b7ae4ce5c2b9c6fefb8e3672b86 https://git.kernel.org/stable/c/71154bbe49423128c1c8577b6576de1ed6836830 https://git.kernel.org/stable/c/79f80a7a47849ef1b3c25a0bedcc448b9cb551c1 https://git.kernel.org/stable/c/b5f46a08269265e2f5e87d855287d6d22de0a32b https://git.kernel.org/stable/c/c9bf315228287653522894df9d851e9b43db9516

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2025-71088", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:30:19.649Z", "datePublished": "2026-01-13T15:34:50.377Z", "dateUpdated": "2026-01-13T15:34:50.377Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-01-13T15:34:50.377Z"}, "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."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/mptcp/options.c", "net/mptcp/protocol.h", "net/mptcp/subflow.c"], "versions": [{"version": "01b7822700f2256900089e00390e119e1ad545df", "lessThan": "b5f46a08269265e2f5e87d855287d6d22de0a32b", "status": "affected", "versionType": "git"}, {"version": "1e777f39b4d75e599a3aac8e0f67d739474f198c", "lessThan": "c9bf315228287653522894df9d851e9b43db9516", "status": "affected", "versionType": "git"}, {"version": "1e777f39b4d75e599a3aac8e0f67d739474f198c", "lessThan": "79f80a7a47849ef1b3c25a0bedcc448b9cb551c1", "status": "affected", "versionType": "git"}, {"version": "1e777f39b4d75e599a3aac8e0f67d739474f198c", "lessThan": "25f1ae942c097b7ae4ce5c2b9c6fefb8e3672b86", "status": "affected", "versionType": "git"}, {"version": "1e777f39b4d75e599a3aac8e0f67d739474f198c", "lessThan": "71154bbe49423128c1c8577b6576de1ed6836830", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/mptcp/options.c", "net/mptcp/protocol.h", "net/mptcp/subflow.c"], "versions": [{"version": "6.2", "status": "affected"}, {"version": "0", "lessThan": "6.2", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.160", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.120", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.65", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.4", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19-rc4", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.110", "versionEndExcluding": "6.1.160"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.120"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.12.65"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.18.4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.19-rc4"}]}]}], "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"}}}}

{"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."}], "id": "CVE-2025-71088", "lastModified": "2026-01-13T16:16:08.460", "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": "Received"}

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