CyberSecBulletin
CVE-2026-64581NVD status: Received

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-64581 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions e8686fd8d18b99f3a9038683045b2f2338a7706d, a9340ebdc13f8bb5063c0bc0b037ee7e640d4ae9, f833821e4b52ab6335d443ede5fb79c38e61d19a as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.12% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to e8686fd8d18b99f3a9038683045b2f2338a7706d or a9340ebdc13f8bb5063c0bc0b037ee7e640d4ae9 or f833821e4b52ab6335d443ede5fb79c38e61d19a or f0ab9a71167bae308e05ab13b65e2007504a603f, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux2b06cdf3e688b98fcc9945873b5d42792bd4eee0 up to, but not including, e8686fd8d18b99f3a9038683045b2f2338a7706d; 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 up to, but not including, a9340ebdc13f8bb5063c0bc0b037ee7e640d4ae9; 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 up to, but not including, f833821e4b52ab6335d443ede5fb79c38e61d19a; 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 up to, but not including, f0ab9a71167bae308e05ab13b65e2007504a603f; 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 up to, but not including, 8dd8929b71c4f06c614f8f54c2cc070453faae16; 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 up to, but not including, 0ea8f06454012d9e7f9c6e6253df710949bf6294; 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 up to, but not including, 96b678d08268b5f5c6fc99d4289d9b7e334fc683; 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 up to, but not including, c283e9ada7fcb7dd4b10592623086b2e6d2f9925; and 13 more rangese8686fd8d18b99f3a9038683045b2f2338a7706d, a9340ebdc13f8bb5063c0bc0b037ee7e640d4ae9, f833821e4b52ab6335d443ede5fb79c38e61d19a, f0ab9a71167bae308e05ab13b65e2007504a603f, 8dd8929b71c4f06c614f8f54c2cc070453faae16, 0ea8f06454012d9e7f9c6e6253df710949bf6294

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official description

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

How developers prevent this class of flaw

  • In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
  • Use thread-safe capabilities such as the data access abstraction in Spring.
  • Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

More Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities (CWE-362)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities

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