CVE Catalog

CVE-2026-98258

HighCVSS 7.8
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.14%

3th percentile - higher than 3% of all known CVEs

Summary

In the Linux kernel, a race condition in POSIX CPU timers can lead to use-after-free (UAF). The issue stems from losing the distinction between 'timer on expiry list' and 'delivery canceled' after changing the 'firing' flag to boolean. The fix checks whether the timer is on the expiry list instead of relying on the flag.

Risk Assessment

An attacker could exploit this vulnerability to gain unauthorized access to kernel memory, potentially leading to privilege escalation or system crash.

Recommendation

Apply the patch from the latest stable Linux kernel release that addresses this issue immediately.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: Prevent freeing a timer which is queued on the expiry list Kijo analyzed another race in the POSIX CPU timer code: Commit bf635681c906 converted cpu_timer::firing from a tristate value to a boolean. This lost the distinction between "not owned by the firing list" and "still owned, but delivery was canceled". The resulting race is: expiry handler timer_settime() timer_delete() -------------- --------------- -------------- collect timer onto private firing list firing = true observes firing = true firing = false return TIMER_RETRY wait for handler observes firing = false finish deletion unhash and free timer resume list traversal read freed elist.next -> UAF The firing bit is clearly the wrong indicator since that commit. Check whether the timer is queued on the expiry list or not instead. If it is queued clear the firing bit to prevent signal delivery as before and return TIMER_RETRY so the caller unlocks the timer which allows the expiry code to make progress and remove it from the list.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS