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CVE-2026-64581 Affecting kernel-livepatch-6.12.103-127.188 package, versions <1:1.0-0.amzn2023

Severity

 Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.12% (2nd percentile)

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  • Snyk IDSNYK-AMZN2023-KERNELLIVEPATCH612103127188-19473900
  • published1 Sept 2026
  • disclosed5 Aug 2026
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Introduced: 5 Aug 2026

CVE-2026-64581  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 kernel-livepatch-6.12.103-127.188 to version 1:1.0-0.amzn2023 or higher.
This issue was patched in ALAS2023-2026-2110.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-livepatch-6.12.103-127.188 package and not the kernel-livepatch-6.12.103-127.188 package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

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.