UBUNTU-CVE-2025-71088

Advisory lineage Upstream: 1 Downstream: 19

Upstream

CVE-2025-71088

Downstream

USN-8179-1 USN-8179-2 USN-8179-3 USN-8179-4 USN-8184-1 USN-8185-1

Published: 13 Jan 2026, 16:16

Last modified:17 Jul 2026, 23:37

Vulnerability Summary

Overall Risk (default)

low

22/100

CVSS Score

5.5 MEDIUM

3.1 (osv_ubuntu)

EPSS Score

No data

KEV

Not listed

Ransomware

No reports

Public exploits

None found

Dark Web

Not detected

Timeline

13 Jan 2026, 16:16

Published

Vulnerability first disclosed

17 Jul 2026, 23:37

Last Modified

Vulnerability information updated

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.

CVSS Metrics

v3.1•MEDIUM•Score: 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Systems

ubuntu•linux
all | all | < 6.8.0-110.110 | < 6.17.0-29.29
ubuntu•linux-allwinner-5.19
all
ubuntu•linux-aws
all | all | < 6.8.0-1052.55 | < 6.17.0-1015.15
ubuntu•linux-aws-5.0
all
ubuntu•linux-aws-5.11
all
ubuntu•linux-aws-5.13
all
ubuntu•linux-aws-5.19
all
ubuntu•linux-aws-5.3
all
ubuntu•linux-aws-5.8
all
ubuntu•linux-aws-6.14
all
ubuntu•linux-aws-6.17
all | < 6.17.0-1017.17~24.04.1
ubuntu•linux-aws-6.2
all
ubuntu•linux-aws-6.5
all
ubuntu•linux-aws-6.8
all | < 6.8.0-1052.55~22.04.1
ubuntu•linux-aws-fips
all | < 6.8.0-1052.55+fips1
ubuntu•linux-azure
all | all | all | < 6.8.0-1054.60 | < 6.17.0-1015.15
ubuntu•linux-azure-5.11
all
ubuntu•linux-azure-5.13
all
ubuntu•linux-azure-5.19
all
ubuntu•linux-azure-5.3
all
ubuntu•linux-azure-5.8
all
ubuntu•linux-azure-6.11
all
ubuntu•linux-azure-6.14
all
ubuntu•linux-azure-6.17
all | < 6.17.0-1015.15~24.04.1
ubuntu•linux-azure-6.2
all
ubuntu•linux-azure-6.5
all
ubuntu•linux-azure-6.8
all | < 6.8.0-1059.65~22.04.1
ubuntu•linux-azure-edge
all
ubuntu•linux-azure-fde
all | all | all
ubuntu•linux-azure-fde-5.19
all
ubuntu•linux-azure-fde-6.14
all
ubuntu•linux-azure-fde-6.17
all
ubuntu•linux-azure-fde-6.2
all
ubuntu•linux-azure-fde-6.8
all
ubuntu•linux-azure-fips
< 6.8.0-1054.60+fips1 | all | < 6.8.0-1053.59+fips1
ubuntu•linux-azure-nvidia
all
ubuntu•linux-azure-nvidia-6.14
all
ubuntu•linux-bluefield
all
ubuntu•linux-fips
all | < 6.8.0-110.110+fips2
ubuntu•linux-gcp
all | all | all | < 6.8.0-1054.57 | < 6.17.0-1018.19
ubuntu•linux-gcp-5.11
all
ubuntu•linux-gcp-5.13
all
ubuntu•linux-gcp-5.19
all
ubuntu•linux-gcp-5.3
all
ubuntu•linux-gcp-5.8
all
ubuntu•linux-gcp-6.11
all
ubuntu•linux-gcp-6.14
all
ubuntu•linux-gcp-6.17
all | < 6.17.0-1018.19~24.04.1
ubuntu•linux-gcp-6.2
all
ubuntu•linux-gcp-6.5
all

Showing first 50 affected entries in server-rendered view.