CVE-2025-68214 — timers: Fix NULL function pointer race in timer_shutdown_sync()
In the Linux kernel, the following vulnerability has been resolved: timers: Fix NULL function pointer race in timer_shutdown_sync() There is a race condition between timer_shutdown_sync() and timer expiration that can lead to hitting a WARN_ON in expire_timers(). The issue occurs when timer_shutdown_sync() clears the timer function to NULL while the timer is still running on another CPU. The race scenario looks like this: CPU0 CPU1 <SOFTIRQ> lock_timer_base() expire_timers() base->running_timer = timer; unlock_timer_base() [call_timer_fn enter] mod_timer() ... timer_shutdown_sync() lock_timer_base() // For now, will not detach the timer but only clear its function to NULL if (base->running_timer != timer) ret = detach_if_pending(timer, base, true); if (shutdown) timer->function = NULL; unlock_timer_base() [call_timer_fn exit] lock_timer_base() base->running_timer = NULL; unlock_timer_base() ... // Now timer is pending while its function set to NULL. // next timer trigger <SOFTIRQ> expire_timers() WARN_ON_ONCE(!fn) // hit ... lock_timer_base() // Now timer will detach if (base->running_timer != timer) ret = detach_if_pending(timer, base, true); if (shutdown) timer->function = NULL; unlock_timer_base() The problem is that timer_shutdown_sync() clears the timer function regardless of whether the timer is currently running. This can leave a pending timer with a NULL function pointer, which triggers the WARN_ON_ONCE(!fn) check in expire_timers(). Fix this by only clearing the timer function when actually detaching the timer. If the timer is running, leave the function pointer intact, which is safe because the timer will be properly detached when it finishes running.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.1% (30-day exploitation probability)+0
- Technical severity (medium)+3
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes matching the vulnerability class (logic error), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux | version 6.2≥ 6.1.158 and < 6.1.159≥ 0cc04e80458a822300b93f82ed861a513edde194 and < 20739af07383e6eb1ec59dcd70b72ebfa9ac362c≥ 0cc04e80458a822300b93f82ed861a513edde194 and < a01efa7a780c42ac5170a949bd95c9786ffcc60a≥ 0cc04e80458a822300b93f82ed861a513edde194 and < 176725f4848376530a0f0da9023f956afcc33585≥ 0cc04e80458a822300b93f82ed861a513edde194 and < 6665fbd7730b26d770c232b20d1b907e6a67a914≥ 334c33aa487be406a149c8b87c38c8399d2dba8d and < 1a975716cc8977f461e45e28e3e5977d46ad7a6a≥ debbcf812d735003c96c5e5968a3cfa4e1fbd1af and < ba43ac025c4318241f8edf94f31d2eebab86991b | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
version 6.18-rc6≥ 6.2 and < 6.6.118version 6.18-rc5version 6.18-rc4version 6.18-rc3version 6.18-rc2version 6.18-rc1version 6.1.158 and 2 more≥ 6.13 and < 6.17.10≥ 6.7 and < 6.12.60 |
Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 4.7 | CVSS 3.1 | Medium | 1.0 | 3.6 | nvd@nist.gov via NIST National Vulnerability Database |
| 4.7 | CVSS 3.1 | Medium | — | — | GitHub, Inc. via GitHub Security Advisories |
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.13%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · linux/linux
- Record published
- Fix documented
- CVSS changed · 4.7
- Source status changed · → Analyzed
- Record created in this database
- 2025
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× References added · Oct 14, 2026 – Oct 14, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
8 on the record
- git.kernel.org/stable/c/6665fbd7730b26d770c232b20d1b907e6a67a914
- git.kernel.org/stable/c/a01efa7a780c42ac5170a949bd95c9786ffcc60a
- git.kernel.org/stable/c/176725f4848376530a0f0da9023f956afcc33585
- git.kernel.org/stable/c/1a975716cc8977f461e45e28e3e5977d46ad7a6a
- git.kernel.org/stable/c/20739af07383e6eb1ec59dcd70b72ebfa9ac362c
- git.kernel.org/stable/c/ba43ac025c4318241f8edf94f31d2eebab86991b
- github.com/advisories/GHSA-q35m-cwfx-j6jx
- nvd.nist.gov/vuln/detail/CVE-2025-68214
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 1d
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 1d
- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 2d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 2d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 2d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 2d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No CISA SSVC assessment.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2025-68214 is "timers: Fix NULL function pointer race in timer_shutdown_sync()", rated Medium. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 4.7 describes technical severity. EPSS 0.13% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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