CVE-2026-64435 audit: Fix data races of skb_queue_len() readers on audit_queue
A data race in the Linux kernel audit subsystem can lead to inconsistent backlog counts, potentially causing denial of service or audit log loss.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64435?
CVE-2026-64435 is a high-severity vulnerability in Linux kernel, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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]
Weakness: CWE-362
Which versions are affected by CVE-2026-64435?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64435?
Apply the vendor's patch.
Is CVE-2026-64435 being exploited?
There is no known exploitation of CVE-2026-64435 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-93584, BELL-CVE-2026-64435, DEBIAN-CVE-2026-64435, GHSA-h4f8-j958-689c, ROOT-OS-DEBIAN-12-CVE-2026-64435, ROOT-OS-UBUNTU-2204-CVE-2026-64435 and 1 more.