CVE-2026-43323: Linux kernel · sched/fair: Fix zero_vruntime tracking fix
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in fb61ffb3fb30a161eb5404c27fc7635e275beafd : update Linux kernel when convenient.
Data as of 6 Nov 2026, 15:49 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-11-06.
- Patch
- Available – fixed in fb61ffb3fb30a161eb5404c27fc7635e275beafd, c089147074ed96ff4330739a0559394c19a3dfc8, 87573883c30f1a8555ff720836bb6ea231058539 +4
Exploitation evidence
Disclosed: evidence found.
CVE published 8 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.
What to do
Upgrade Linux to fb61ffb3fb30a161eb5404c27fc7635e275beafd, c089147074ed96ff4330739a0559394c19a3dfc8, 87573883c30f1a8555ff720836bb6ea231058539 or 1319ea57529e131822bab56bf417c8edc2db9ae8; Linux to 6.19.12, 6.18.22 or 6.12.81.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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Description
In the Linux kernel, the following vulnerability has been resolved: sched/fair: Fix zero_vruntime tracking fix John reported that stress-ng-yield could make his machine unhappy and managed to bisect it to commit b3d99f43c72b ("sched/fair: Fix zero_vruntime tracking"). The combination of yield and that commit was specific enough to hypothesize the following scenario: Suppose we have 2 runnable tasks, both doing yield. Then one will be eligible and one will not be, because the average position must be in between these two entities. Therefore, the runnable task will be eligible, and be promoted a full slice (all the tasks do is yield after all). This causes it to jump over the other task and now the other task is eligible and current is no longer. So we schedule. Since we are runnable, there is no {de,en}queue. All we have is the __{en,de}queue_entity() from {put_prev,set_next}_task(). But per the fingered commit, those two no longer move zero_vruntime. All that moves zero_vruntime are tick and full {de,en}queue. This means, that if the two tasks playing leapfrog can reach the critical speed to reach the overflow point inside one tick's worth of time, we're up a creek. Additionally, when multiple cgroups are involved, there is no guarantee the tick will in fact hit every cgroup in a timely manner. Statistically speaking it will, but that same statistics does not rule out the possibility of one cgroup not getting a tick for a significant amount of time -- however unlikely. Therefore, just like with the yield() case, force an update at the end of every slice. This ensures the update is never more than a single slice behind and the whole thing is within 2 lag bounds as per the comment on entity_key().
References
- git.kernel.org/stable/c/c089147074ed96ff4330739a0559394c19a3dfc8 (opens in a new tab)
- git.kernel.org/stable/c/87573883c30f1a8555ff720836bb6ea231058539 (opens in a new tab)
- git.kernel.org/stable/c/fb61ffb3fb30a161eb5404c27fc7635e275beafd (opens in a new tab)
- git.kernel.org/stable/c/1319ea57529e131822bab56bf417c8edc2db9ae8 (opens in a new tab)