VulnerabilityPublished 3 Nov 2026

CVE-2026-99256: Linux kernel · dm cache: fix issue with background work locking

Source GCVE Database

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Authoritative record:CVE-2026-99256· Medium

Not known to be exploited · fixed in f5db935d257023c3ef410bd39163b949b0e5a55d : update Linux kernel when convenient.

Data as of 3 Nov 2026, 13:15 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Patch: Available – fixed in f5db935d257023c3ef410bd39163b949b0e5a55d, bc9781c0247de107876f32929f1637db93a42b34, 6290507ecc0dd6dd40759729cbbbd49b1d2a63c4 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Nov 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 3 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-pr5p-x5rg-2942

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ b29d4986d0da1a27cd35917cdb433672f5c95d7f, < f5db935d257023c3ef410bd39163b949b0e5a55d	Fixed in f5db935d257023c3ef410bd39163b949b0e5a55d
LinuxLinux	Affected ≥ b29d4986d0da1a27cd35917cdb433672f5c95d7f, < bc9781c0247de107876f32929f1637db93a42b34	Fixed in bc9781c0247de107876f32929f1637db93a42b34
LinuxLinux	Affected ≥ b29d4986d0da1a27cd35917cdb433672f5c95d7f, < 6290507ecc0dd6dd40759729cbbbd49b1d2a63c4	Fixed in 6290507ecc0dd6dd40759729cbbbd49b1d2a63c4
LinuxLinux	Affected ≥ b29d4986d0da1a27cd35917cdb433672f5c95d7f, < 8433fd005c25fd127021f67c9144a879fb585572	Fixed in 8433fd005c25fd127021f67c9144a879fb585572
LinuxLinux	Affected ≥ b29d4986d0da1a27cd35917cdb433672f5c95d7f, < 104f09e02038b0fc6bbb718b3976af029e15c1d0	Fixed in 104f09e02038b0fc6bbb718b3976af029e15c1d0
LinuxLinux	Affected ≥ b29d4986d0da1a27cd35917cdb433672f5c95d7f, < 73df2ff409f3db95029982fe3656329568e3715d	Fixed in 73df2ff409f3db95029982fe3656329568e3715d

AI-suggested

A fix has been implemented by replacing the rw_semaphore with a spinlock and wait queue in the dm cache code. Users should apply the updated Linux kernel version containing this fix once available. No additional mitigation steps are specified.

Description

A locking issue in the Linux kernel's dm cache component was fixed. The vulnerability involved improper use of a rw_semaphore for background work locking, where the process unlocking was not guaranteed to be the same as the locking process, causing kernel warnings and potential instability. The fix replaced the rw_semaphore with a spinlock and wait queue mechanism.

References

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