CyberSecBulletin
CVE-2026-64435NVD status: Modified

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-64435 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 8.2 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 69f98fff30bdaa72b0cb0e7e078ab6456a0a59b0, b35597bdae1a5d8395da4b9baa993b9b71f74d68, e575dabb805252e3113fdc3f56f6ecacfde422d0 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 0.33% 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 69f98fff30bdaa72b0cb0e7e078ab6456a0a59b0 or b35597bdae1a5d8395da4b9baa993b9b71f74d68 or e575dabb805252e3113fdc3f56f6ecacfde422d0 or 7ff42312ccde549f8c698723822c7db35107a39b, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.261 or 5.15.212 or 6.1.178 or 6.6.145, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux3197542482df22c2a131d4a813280bd7c54cedf5 up to, but not including, 69f98fff30bdaa72b0cb0e7e078ab6456a0a59b0; 3197542482df22c2a131d4a813280bd7c54cedf5 up to, but not including, b35597bdae1a5d8395da4b9baa993b9b71f74d68; 3197542482df22c2a131d4a813280bd7c54cedf5 up to, but not including, e575dabb805252e3113fdc3f56f6ecacfde422d0; 3197542482df22c2a131d4a813280bd7c54cedf5 up to, but not including, 7ff42312ccde549f8c698723822c7db35107a39b; 3197542482df22c2a131d4a813280bd7c54cedf5 up to, but not including, a3d85dec60bb0622360fc176b2a51abdbe2ff0ad; 3197542482df22c2a131d4a813280bd7c54cedf5 up to, but not including, fe997a84a385f840b593ead92e575503a5046cee; 3197542482df22c2a131d4a813280bd7c54cedf5 up to, but not including, c5186201fa7030289cc4fe23fae87a3fcb566856; 3197542482df22c2a131d4a813280bd7c54cedf5 up to, but not including, c9a71daaecb2fb1d8c704545cc0b1c920b9bf5d7; and 1 more ranges69f98fff30bdaa72b0cb0e7e078ab6456a0a59b0, b35597bdae1a5d8395da4b9baa993b9b71f74d68, e575dabb805252e3113fdc3f56f6ecacfde422d0, 7ff42312ccde549f8c698723822c7db35107a39b, a3d85dec60bb0622360fc176b2a51abdbe2ff0ad, fe997a84a385f840b593ead92e575503a5046cee
LinuxLinux Kernel4.10 up to, but not including, 5.10.261; 5.11 up to, but not including, 5.15.212; 5.16 up to, but not including, 6.1.178; 6.2 up to, but not including, 6.6.145; 6.7 up to, but not including, 6.12.96; 6.13 up to, but not including, 6.18.39; 6.19 up to, but not including, 7.1.4; 7.25.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, 6.18.39

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
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
LowLimited modification of data is possible.
Availability
HighThe component can be taken down completely.

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

Official description

In the Linux kernel, the following vulnerability has been resolved: audit: Fix data races of skb_queue_len() readers on audit_queue Multiple readers access audit_queue.qlen via skb_queue_len() without holding the queue lock or using READ_ONCE(), while kauditd writes to this field via the skb_dequeue() → __skb_unlink() path with WRITE_ONCE() protected by a spinlock. This constitutes data races. All affected skb_queue_len(&audit_queue) call sites: - kauditd_thread() wait_event_freezable() condition - audit_receive_msg() AUDIT_GET handler (s.backlog assignment) - audit_receive() backlog check - audit_log_start() backlog check and pr_warn() KCSAN reports the following conflicting access pattern (one example): ================================================================== BUG: KCSAN: data-race in audit_log_start / skb_dequeue write (marked) to 0xffffffff8512ee20 of 4 bytes by task 661 on cpu 57: skb_dequeue+0x70/0xf0 kauditd_send_queue+0x71/0x220 kauditd_thread+0x1cb/0x430 kthread+0x1c2/0x210 ret_from_fork+0x162/0x1a0 ret_from_fork_asm+0x1a/0x30 read to 0xffffffff8512ee20 of 4 bytes by task 36586 on cpu 1: audit_log_start+0x2a0/0x6b0 audit_core_dumps+0x64/0xa0 do_coredump+0x14b/0x1260 get_signal+0xeb2/0xf70 arch_do_signal_or_restart+0x41/0x170 exit_to_user_mode_loop+0xa2/0x1c0 do_syscall_64+0x1a3/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0xe0 value changed: 0x00000001 -> 0x00000000 ================================================================== Resolve the race by switching to lockless helper skb_queue_len_lockless(), which internally uses READ_ONCE() and properly pairs with the WRITE_ONCE() write accesses already present on the writer side. [PM: line length tweak]

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: yes, technical impact: partial).
  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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