CVE-2026-98258: posix-cpu-timers: Prevent freeing a timer which is queued on the expiry list
Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.
Generated by VEDAS. Scores as of 2026-11-04 15:41 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.
What it is
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.
Description quoted from the CVE record (assigned by Linux, published 2026-10-06).
How it can be exploited
Exploitable with local access with low attack complexity needing low privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Public exploit evidence (Exploit Observer)
Exploit Observer found 1 code repository naming this CVE.
Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.
See all 7 references on Exploit Observer
Live scores
- EPSS
- 0.001
low predicted chance of attack - VEDAS
- 0.970
strong exploit evidence - On CISA KEV
- Not listed
- Detection rule
- No public rule yet
Who is affected
| Product | Affected | Not affected |
|---|---|---|
| Linux | from bf635681c906 before 9971dac1a778 (git commit) from bf635681c906 before 4336e3f47d9d (git commit) from bf635681c906 before c21eaa72f02f (git commit) | Not stated |
| Linux | version 6.13 | 0 is not affected (up to 6.13); 6.18.54 is not affected; 7.2.8 is not affected; 7.3 is not affected |
Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.
How to fix it
No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.
How to detect it
There is no open VEDAS detection rule for this bug yet. It is listed on the detection gaps page if CISA has confirmed attacks.
References
Other references
- https://git.kernel.org/stable/c/9971dac1a77845ff467146915fcbb9170f6a8209
- https://git.kernel.org/stable/c/4336e3f47d9d516441066e9a65eaf076790d8d45
- https://git.kernel.org/stable/c/c21eaa72f02fc6e85621cbe09d303d8fb8bd39cd
Other databases
Where this comes from
This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.
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