CVE-2026-23274 netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels
A local attacker can cause a kernel panic by reusing an uninitialized timer label in netfilter IDLETIMER rules, requiring panic_on_warn enabled.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-23274?
CVE-2026-23274 is a high-severity vulnerability in Linux kernel, published on 20 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels
IDLETIMER revision 0 rules reuse existing timers by label and always call mod_timer() on timer->timer.
If the label was created first by revision 1 with XT_IDLETIMER_ALARM, the object uses alarm timer semantics and timer->timer is never initialized. Reusing that object from revision 0 causes mod_timer() on an uninitialized timer_list, triggering debugobjects warnings and possible panic when panic_on_warn=1.
Fix this by rejecting revision 0 rule insertion when an existing timer with the same label is of ALARM type.
Weakness: CWE-758
Which versions are affected by CVE-2026-23274?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23274?
Apply the vendor's patch.
Is CVE-2026-23274 being exploited?
There is no known exploitation of CVE-2026-23274 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-80201, BELL-CVE-2026-23274, DEBIAN-CVE-2026-23274, GHSA-3cwp-73f3-j7w3, ROOT-OS-DEBIAN-11-CVE-2026-23274, ROOT-OS-DEBIAN-12-CVE-2026-23274 and 4 more.