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CVE.org (no NVD analysis yet)· CNA Linux

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

Noroxi assessment

Priority: Monitor (action score 0/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.20% (FIRST EPSS).
  • Fixed version: Linux Linux 0c7a8cad7c96012a9157a189649e569d0390f384, 104f09e02038b0fc6bbb718b3976af029e15c1d0, 2f2cfa16dd0f4179bb988139dd37d00a42324f6c.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 0c7a8cad7c96012a9157a189649e569d0390f384, 104f09e02038b0fc6bbb718b3976af029e15c1d0, 2f2cfa16dd0f4179bb988139dd37d00a42324f6c or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: dm cache: fix issue with background work locking dm cache used a rw_semaphore for background_work_lock. Write locks on rw_semaphores have strict owner semantics, but there was no guarantee that the process that locked background_work_lock was the same process that unlocked it. This can be easily seen using a kernel compiled with CONFIG_DEBUG_RWSEMS. Given a dm cache device <cache>, run: 'dmsetup suspend <cache> && dmsetup resume <cache>'. This will trigger a kernel warning: DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)) triggered by cache_resume(). To fix this, switch from a rw_semaphore to a spinlock and a wait queue. dm cache already has a wait queue and associated counter, migration_wait and nr_allocated_migrations, that was getting woken up when background work was getting completed, but wasn't actually used by anything. This is replaced by the background_work queue and counter.

—No exploit Fix available
Published
Nov 3, 2026
Updated
Nov 3, 2026
EPSS
0.2% · 10th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

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  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 4.12affected
    • b29d4986d0da1a27cd35917cdb433672f5c95d7f and later · before 0c7a8cad7c96012a9157a189649e569d0390f384affected · git
    • b29d4986d0da1a27cd35917cdb433672f5c95d7f and later · before f5db935d257023c3ef410bd39163b949b0e5a55daffected · git
    • b29d4986d0da1a27cd35917cdb433672f5c95d7f and later · before 6290507ecc0dd6dd40759729cbbbd49b1d2a63c4affected · git
    • b29d4986d0da1a27cd35917cdb433672f5c95d7f and later · before 8433fd005c25fd127021f67c9144a879fb585572affected · git
    • b29d4986d0da1a27cd35917cdb433672f5c95d7f and later · before 2f2cfa16dd0f4179bb988139dd37d00a42324f6caffected · git
    • b29d4986d0da1a27cd35917cdb433672f5c95d7f and later · before 73df2ff409f3db95029982fe3656329568e3715daffected · git
    • b29d4986d0da1a27cd35917cdb433672f5c95d7f and later · before 104f09e02038b0fc6bbb718b3976af029e15c1d0affected · git
    • b29d4986d0da1a27cd35917cdb433672f5c95d7f and later · before bc9781c0247de107876f32929f1637db93a42b34affected · git
    • before 4.12not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.115-16.12.115-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-99254Nov 3, 2026 · io_uring: don't flood a cancelling task with task_work
    0Monitor
  • ← EarlierCVE-2026-99255Nov 3, 2026 · io_uring/io-wq: don't hide a link from cancellations
    0Monitor
  • Later →CVE-2026-99257Nov 3, 2026 · gpio: shared: gracefully handle no-device lookup of shared GPIOs
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux0c7a8cad7c96012a9157a189649e569d0390f384Vendor (CNA)
Linux Linux104f09e02038b0fc6bbb718b3976af029e15c1d0Vendor (CNA)
Linux Linux2f2cfa16dd0f4179bb988139dd37d00a42324f6cVendor (CNA)
Linux Linux6290507ecc0dd6dd40759729cbbbd49b1d2a63c4Vendor (CNA)
Linux Linux73df2ff409f3db95029982fe3656329568e3715dVendor (CNA)
Linux Linux8433fd005c25fd127021f67c9144a879fb585572Vendor (CNA)
Linux Linuxbc9781c0247de107876f32929f1637db93a42b34Vendor (CNA)
Linux Linuxf5db935d257023c3ef410bd39163b949b0e5a55dVendor (CNA)
debian:linux6.12.115-1 · Debian:13Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 5, 2026+2 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Exploit maturity— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records