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CVE-2026-64581

xfrm: fix sk_dst_cache double-free in xfrm_user_policy()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 3.17, 4.5, 3.19, 4.2, 4.10, and 7 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

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, 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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 · fixed in e8686fd8d18b99f3a9038683045b2f2338a7706d; From 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 · fixed in a9340ebdc13f8bb5063c0bc0b037ee7e640d4ae9; From 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 · fixed in f833821e4b52ab6335d443ede5fb79c38e61d19a; From 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 · fixed in f0ab9a71167bae308e05ab13b65e2007504a603f; From 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 · fixed in 8dd8929b71c4f06c614f8f54c2cc070453faae16; From 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 · fixed in 0ea8f06454012d9e7f9c6e6253df710949bf6294; From 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 · fixed in 96b678d08268b5f5c6fc99d4289d9b7e334fc683; From 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 · fixed in c283e9ada7fcb7dd4b10592623086b2e6d2f9925; From 3.16.52 · fixed in 3.17; From 4.4.163 · fixed in 4.5; From 3.18.101 · fixed in 3.19; From 4.1.52 · fixed in 4.2; From 4.4.123 · fixed in 4.5; From 4.9.89 · fixed in 4.10

  • Linux Linux

    4.14

  • KernelLinux

    From 4.14.0 · fixed in 5.10.267; From 5.11.0 · fixed in 5.15.218; From 5.16.0 · fixed in 6.1.185; From 6.2.0 · fixed in 6.6.154; From 6.7.0 · fixed in 6.12.106; From 6.13.0 · fixed in 6.18.47; From 6.19.0 · fixed in 7.1.6

References 8

git.kernel.org