linux-cve-announce - CVE-2025-71144: mptcp: ensure context reset on disconnect()

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Message-ID: <2026011459-CVE-2025-71144-8a18@gregkh>
Date: Wed, 14 Jan 2026 16:09:00 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-71144: mptcp: ensure context reset on disconnect()

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

mptcp: ensure context reset on disconnect()

After the blamed commit below, if the MPC subflow is already in TCP_CLOSE
status or has fallback to TCP at mptcp_disconnect() time,
mptcp_do_fastclose() skips setting the `send_fastclose flag` and the later
__mptcp_close_ssk() does not reset anymore the related subflow context.

Any later connection will be created with both the `request_mptcp` flag
and the msk-level fallback status off (it is unconditionally cleared at
MPTCP disconnect time), leading to a warning in subflow_data_ready():

  WARNING: CPU: 26 PID: 8996 at net/mptcp/subflow.c:1519 subflow_data_ready (net/mptcp/subflow.c:1519 (discriminator 13))
  Modules linked in:
  CPU: 26 UID: 0 PID: 8996 Comm: syz.22.39 Not tainted 6.18.0-rc7-05427-g11fc074f6c36 #1 PREEMPT(voluntary)
  Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
  RIP: 0010:subflow_data_ready (net/mptcp/subflow.c:1519 (discriminator 13))
  Code: 90 0f 0b 90 90 e9 04 fe ff ff e8 b7 1e f5 fe 89 ee bf 07 00 00 00 e8 db 19 f5 fe 83 fd 07 0f 84 35 ff ff ff e8 9d 1e f5 fe 90 <0f> 0b 90 e9 27 ff ff ff e8 8f 1e f5 fe 4c 89 e7 48 89 de e8 14 09
  RSP: 0018:ffffc9002646fb30 EFLAGS: 00010293
  RAX: 0000000000000000 RBX: ffff88813b218000 RCX: ffffffff825c8435
  RDX: ffff8881300b3580 RSI: ffffffff825c8443 RDI: 0000000000000005
  RBP: 000000000000000b R08: ffffffff825c8435 R09: 000000000000000b
  R10: 0000000000000005 R11: 0000000000000007 R12: ffff888131ac0000
  R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
  FS:  00007f88330af6c0(0000) GS:ffff888a93dd2000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f88330aefe8 CR3: 000000010ff59000 CR4: 0000000000350ef0
  Call Trace:
   <TASK>
   tcp_data_ready (net/ipv4/tcp_input.c:5356)
   tcp_data_queue (net/ipv4/tcp_input.c:5445)
   tcp_rcv_state_process (net/ipv4/tcp_input.c:7165)
   tcp_v4_do_rcv (net/ipv4/tcp_ipv4.c:1955)
   __release_sock (include/net/sock.h:1158 (discriminator 6) net/core/sock.c:3180 (discriminator 6))
   release_sock (net/core/sock.c:3737)
   mptcp_sendmsg (net/mptcp/protocol.c:1763 net/mptcp/protocol.c:1857)
   inet_sendmsg (net/ipv4/af_inet.c:853 (discriminator 7))
   __sys_sendto (net/socket.c:727 (discriminator 15) net/socket.c:742 (discriminator 15) net/socket.c:2244 (discriminator 15))
   __x64_sys_sendto (net/socket.c:2247)
   do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
  RIP: 0033:0x7f883326702d

Address the issue setting an explicit `fastclosing` flag at fastclose
time, and checking such flag after mptcp_do_fastclose().

The Linux kernel CVE team has assigned CVE-2025-71144 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.6.119 with commit 3a13454fd098ed51e733958488f8ec62859a9ed8 and fixed in 6.6.120 with commit 5c7c7135468f3fc6379cde9777a2c18bfe92d82f
	Issue introduced in 6.12.60 with commit f6fb2cbc91a81178dea23d463503b4525a76825d and fixed in 6.12.65 with commit 1c7c3a9314d8a7fc0e9a508606466a967c8e774a
	Issue introduced in 6.18 with commit ae155060247be8dcae3802a95bd1bdf93ab3215d and fixed in 6.18.5 with commit f1a77dfc3b045c3dd5f6e64189b9f52b90399f07
	Issue introduced in 6.18 with commit ae155060247be8dcae3802a95bd1bdf93ab3215d and fixed in 6.19-rc4 with commit 86730ac255b0497a272704de9a1df559f5d6602e
	Issue introduced in 6.1.159 with commit 9ea05fabce31ff93a0adae8221c58bc6d7b832f3
	Issue introduced in 6.17.10 with commit c4f7b0916b95fd2226e5ab98882482b08f52e1c0

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-71144
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/mptcp/protocol.c
	net/mptcp/protocol.h


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/5c7c7135468f3fc6379cde9777a2c18bfe92d82f
	https://git.kernel.org/stable/c/1c7c3a9314d8a7fc0e9a508606466a967c8e774a
	https://git.kernel.org/stable/c/f1a77dfc3b045c3dd5f6e64189b9f52b90399f07
	https://git.kernel.org/stable/c/86730ac255b0497a272704de9a1df559f5d6602e