---
id: CVE-2026-64581
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xfrm: fix sk_dst_cache double-free in xfrm_user_policy()

  xfrm_user_policy() clears the socket dst cache with __sk_dst_reset(),
  i.e
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xfrm: fix sk_dst_cache double-free in xfrm_user_policy()

  xfrm_user_policy() clears the socket dst cache with __sk_dst_reset(),
  i.e. the non-atomic __sk_dst_set(sk, NUL…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
published: '2026-08-05'
updated: '2026-08-08'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-64581'
references:
  - url: 'https://git.kernel.org/stable/c/96b678d08268b5f5c6fc99d4289d9b7e334fc683'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c283e9ada7fcb7dd4b10592623086b2e6d2f9925'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e8686fd8d18b99f3a9038683045b2f2338a7706d'
  - url: 'https://git.kernel.org/stable/c/a9340ebdc13f8bb5063c0bc0b037ee7e640d4ae9'
  - url: 'https://git.kernel.org/stable/c/f833821e4b52ab6335d443ede5fb79c38e61d19a'
  - url: 'https://git.kernel.org/stable/c/f0ab9a71167bae308e05ab13b65e2007504a603f'
  - url: 'https://git.kernel.org/stable/c/8dd8929b71c4f06c614f8f54c2cc070453faae16'
  - url: 'https://git.kernel.org/stable/c/0ea8f06454012d9e7f9c6e6253df710949bf6294'
tags:
  - nvd
  - cve.org
epss: 0.00121
epssPercentile: 0.01924
ingestedAt: '2026-08-08T21:30:13.001Z'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <
    e8686fd8d18b99f3a9038683045b2f2338a7706d
  - >-
    Linux >= 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <
    a9340ebdc13f8bb5063c0bc0b037ee7e640d4ae9
  - >-
    Linux >= 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <
    f833821e4b52ab6335d443ede5fb79c38e61d19a
  - >-
    Linux >= 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <
    f0ab9a71167bae308e05ab13b65e2007504a603f
  - >-
    Linux >= 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <
    8dd8929b71c4f06c614f8f54c2cc070453faae16
  - >-
    Linux >= 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <
    0ea8f06454012d9e7f9c6e6253df710949bf6294
  - >-
    Linux >= 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <
    96b678d08268b5f5c6fc99d4289d9b7e334fc683
  - >-
    Linux >= 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <
    c283e9ada7fcb7dd4b10592623086b2e6d2f9925
  - Linux 72f157be2f81910ae759bfe2e5c2256fc4625645
  - Linux 9e9fe58a92a46c6d154d2901735bf230d91b8507
  - Linux adc1ec6cdc20d430aa01b86497220709b9149466
  - Linux b54033eb1cfd77aba471269ddd804ed8d3e35dea
  - Linux c9e82cb34c3c2ee895af01bc899c6ed0bc6eb04a
  - Linux 5eef9b51114fcc65651d671add52f267f91b9451
  - Linux >= 3.16.52 < 3.17
  - Linux >= 4.4.163 < 4.5
  - Linux >= 3.18.101 < 3.19
  - Linux >= 4.1.52 < 4.2
  - Linux >= 4.4.123 < 4.5
  - Linux >= 4.9.89 < 4.10
  - Linux 4.14
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T15:43:16.753183Z'
---

## Overview

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

xfrm: fix sk_dst_cache double-free in xfrm_user_policy()

xfrm_user_policy() clears the socket dst cache with __sk_dst_reset(),
i.e. the non-atomic __sk_dst_set(sk, NULL): it reads sk_dst_cache with
rcu_dereference_protected(), stores NULL and dst_release()s the old dst.
That is only safe if no other thread modifies sk_dst_cache concurrently.

For a connected UDP socket that does not hold: the transmit fast path
(udp_sendmsg -> sk_dst_check -> sk_dst_reset) resets the cache locklessly
with an atomic xchg(). A per-socket policy change racing a send can make
both sides observe the same old dst and each dst_release() it, dropping
the socket's single reference twice and freeing the xfrm_dst bundle while
it is still referenced:

  BUG: KASAN: slab-use-after-free in dst_release
  Write of size 4 at addr ffff88801897b6c0 by task exploit/155
  Call Trace:
   ...
   dst_release (... ./include/linux/rcuref.h:109)
   xfrm_user_policy (./include/net/sock.h:2239 ./include/net/sock.h:2256 net/xfrm/xfrm_state.c:3053)
   do_ip_setsockopt (net/ipv4/ip_sockglue.c:1347)
   ip_setsockopt (net/ipv4/ip_sockglue.c:1417)
   do_sock_setsockopt (net/socket.c:2368)
   __sys_setsockopt (net/socket.c:2393)
   __x64_sys_setsockopt (net/socket.c:2396)
   do_syscall_64 (arch/x86/entry/syscall_64.c:94)
   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)

Reachable by an unprivileged user via a user+network namespace.

Use the atomic sk_dst_reset() so the cache is cleared and released with a
single xchg(): whichever side wins releases the dst once, the other sees
NULL and does nothing. Behaviour is otherwise unchanged.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.