---
id: CVE-2025-23145
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mptcp: fix NULL pointer in can_accept_new_subflow

  When testing valkey benchmark tool with MPTCP, the kernel panics in
  'mptcp_can_accept_new_subflow' because subflow_re…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mptcp: fix NULL pointer in can_accept_new_subflow

  When testing valkey benchmark tool with MPTCP, the kernel panics in
  'mptcp_can_accept_new_subflow' because subflow_re…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-476
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.9, < 5.10.237'
  - 'linux_kernel >= 5.11, < 5.15.181'
  - 'linux_kernel >= 5.16, < 6.1.135'
  - 'linux_kernel >= 6.2, < 6.6.88'
  - 'linux_kernel >= 6.7, < 6.12.24'
  - 'linux_kernel >= 6.13, < 6.13.12'
  - 'linux_kernel >= 6.14, < 6.14.3'
  - debian_linux = 11.0
patched:
  - linux_kernel 6.14.3
published: '2025-05-01'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:18:16.510'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-23145'
references:
  - url: 'https://git.kernel.org/stable/c/443041deb5ef6a1289a99ed95015ec7442f141dc'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4b2649b9717678aeb097893cc49f59311a1ecab0'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7f9ae060ed64aef8f174c5f1ea513825b1be9af1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/855bf0aacd51fced11ea9aa0d5101ee0febaeadb'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8cf7fef1bb2ffea7792bcbf71ca00216cecc725d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b3088bd2a6790c8efff139d86d7a9d0b1305977b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/dc81e41a307df523072186b241fa8244fecd7803'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/efd58a8dd9e7a709a90ee486a4247c923d27296f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
  - cve.org
epss: 0.00576
epssPercentile: 0.47301
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-15T21:44:47.460002Z'
ingestedAt: '2026-10-15T22:48:25.476Z'
---

## Overview

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

mptcp: fix NULL pointer in can_accept_new_subflow

When testing valkey benchmark tool with MPTCP, the kernel panics in
'mptcp_can_accept_new_subflow' because subflow_req->msk is NULL.

Call trace:

  mptcp_can_accept_new_subflow (./net/mptcp/subflow.c:63 (discriminator 4)) (P)
  subflow_syn_recv_sock (./net/mptcp/subflow.c:854)
  tcp_check_req (./net/ipv4/tcp_minisocks.c:863)
  tcp_v4_rcv (./net/ipv4/tcp_ipv4.c:2268)
  ip_protocol_deliver_rcu (./net/ipv4/ip_input.c:207)
  ip_local_deliver_finish (./net/ipv4/ip_input.c:234)
  ip_local_deliver (./net/ipv4/ip_input.c:254)
  ip_rcv_finish (./net/ipv4/ip_input.c:449)
  ...

According to the debug log, the same req received two SYN-ACK in a very
short time, very likely because the client retransmits the syn ack due
to multiple reasons.

Even if the packets are transmitted with a relevant time interval, they
can be processed by the server on different CPUs concurrently). The
'subflow_req->msk' ownership is transferred to the subflow the first,
and there will be a risk of a null pointer dereference here.

This patch fixes this issue by moving the 'subflow_req->msk' under the
`own_req == true` conditional.

Note that the !msk check in subflow_hmac_valid() can be dropped, because
the same check already exists under the own_req mpj branch where the
code has been moved to.

## Affected

- `linux_kernel >= 5.9, < 5.10.237`
- `linux_kernel >= 5.11, < 5.15.181`
- `linux_kernel >= 5.16, < 6.1.135`
- `linux_kernel >= 6.2, < 6.6.88`
- `linux_kernel >= 6.7, < 6.12.24`
- `linux_kernel >= 6.13, < 6.13.12`
- `linux_kernel >= 6.14, < 6.14.3`
- `debian_linux = 11.0`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.14.3`