xfrm: fix sk_dst_cache double-free in xfrm_user_policy()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-64581
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-05 08:16:38 UTC
Updated2026-08-05 08:16:38 UTC
DescriptionIn 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.

Risk And Classification

EPSS: 0.001450000 probability, percentile 0.042100000 (date 2026-08-05)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 96b678d08268b5f5c6fc99d4289d9b7e334fc683 git Not specified
CNA Linux Linux affected 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 c283e9ada7fcb7dd4b10592623086b2e6d2f9925 git Not specified
CNA Linux Linux affected 72f157be2f81910ae759bfe2e5c2256fc4625645 git Not specified
CNA Linux Linux affected 9e9fe58a92a46c6d154d2901735bf230d91b8507 git Not specified
CNA Linux Linux affected adc1ec6cdc20d430aa01b86497220709b9149466 git Not specified
CNA Linux Linux affected b54033eb1cfd77aba471269ddd804ed8d3e35dea git Not specified
CNA Linux Linux affected c9e82cb34c3c2ee895af01bc899c6ed0bc6eb04a git Not specified
CNA Linux Linux affected 5eef9b51114fcc65651d671add52f267f91b9451 git Not specified
CNA Linux Linux affected 3.16.52 3.17 semver Not specified
CNA Linux Linux affected 4.4.163 4.5 semver Not specified
CNA Linux Linux affected 3.18.101 3.19 semver Not specified
CNA Linux Linux affected 4.1.52 4.2 semver Not specified
CNA Linux Linux affected 4.4.123 4.5 semver Not specified
CNA Linux Linux affected 4.9.89 4.10 semver Not specified
CNA Linux Linux affected 4.14 Not specified
CNA Linux Linux unaffected 4.14 semver Not specified
CNA Linux Linux unaffected 7.1.6 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc4 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/96b678d08268b5f5c6fc99d4289d9b7e334fc683 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c283e9ada7fcb7dd4b10592623086b2e6d2f9925 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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