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NVD / CVE Program· CNA Linux

CVE-2026-89654: ceph: fix UAF in check_new_map() on session freed during unlock

Noroxi assessment

Priority: Monitor (action score 39/100)

  • 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: 0.67% (FIRST EPSS); higher than 52% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 21d5be092d947f8d83f76f7ebf3989e7e9230a98, 352a278d5a1965aae3f817ce5d24a67ee42d45d1, 820871e9dbeecd2533c4c5f5d91878ceaf02324c.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 21d5be092d947f8d83f76f7ebf3989e7e9230a98, 352a278d5a1965aae3f817ce5d24a67ee42d45d1, 820871e9dbeecd2533c4c5f5d91878ceaf02324c 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: ceph: fix UAF in check_new_map() on session freed during unlock check_new_map() iterates mdsc->sessions[] and for each active session drops mdsc->mutex to perform per-session operations. The forced-close path (rank removed from map) correctly takes a reference on s via ceph_get_mds_session() before releasing mdsc->mutex, but three other paths do not: Path A (address changed): mutex_unlock → mutex_lock(&s->s_mutex) Path B (reconnect): mutex_unlock → send_mds_reconnect(mdsc, s) Path C (active transition): mutex_unlock → mutex_lock(&s->s_mutex) Without the extra reference, another thread can acquire mdsc->mutex during the unlock window, call __unregister_session() which drops the last reference on s, and free it. The original thread then accesses freed memory via s->s_mutex. Fix by adding ceph_get_mds_session(s) before each mutex_unlock and ceph_put_mds_session(s) after the corresponding mutex_lock, matching the pattern already used in the forced-close path. Race timeline (Path A): Thread A (check_new_map) Thread B (another map update holds mdsc->mutex or session teardown) -------------------------- -------------------------- s = mdsc->sessions[i] (refcount == 1, held only by sessions[] array) mutex_unlock(&mdsc->mutex) ---> acquires mdsc->mutex __unregister_session(mdsc, s) sessions[i] = NULL ceph_put_mds_session(s) refcount: 1 -> 0 kfree(s) <--- freed! mutex_lock(&s->s_mutex) UAF on freed s->s_mutex

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Sep 11, 2026
Updated
Oct 30, 2026
EPSS
0.6% · 52th percentile
CWE
—

Report tools

JSON

Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.6%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
9.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-89654

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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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.

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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

    • 2.6.34affected
    • 2f2dc053404febedc9c273452d9d518fb31fde72 and later · before 989343b7ee5b1a08778be0c7c4bf6030d3910807affected · git
    • 2f2dc053404febedc9c273452d9d518fb31fde72 and later · before 352a278d5a1965aae3f817ce5d24a67ee42d45d1affected · git
    • 2f2dc053404febedc9c273452d9d518fb31fde72 and later · before 820871e9dbeecd2533c4c5f5d91878ceaf02324caffected · git
    • 2f2dc053404febedc9c273452d9d518fb31fde72 and later · before 9646dfee880730aae4b379a4b8ee6c88ac735acdaffected · git
    • 2f2dc053404febedc9c273452d9d518fb31fde72 and later · before 21d5be092d947f8d83f76f7ebf3989e7e9230a98affected · git
    • 2f2dc053404febedc9c273452d9d518fb31fde72 and later · before ee611a7509554c4ca1f54f6aefe592fb1df7ea70affected · git
    • before 2.6.34not affected · semver
    • 6.1.191 and later · up to and including 6.1.*not affected · semver
    • 6.6.160 and later · up to and including 6.6.*not 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:14linuxbefore 7.2.6-17.2.6-1

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-2026-89652Sep 11, 2026 · ceph: bound copied dentry name length in NFS export get_name
    39Monitor
  • ← EarlierCVE-2026-89653Sep 11, 2026 · ceph: reject export_targets ranks >= CEPH_MAX_MDS in mdsmap decode
    39Monitor
  • Later →CVE-2026-89655Sep 11, 2026 · ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
    39Monitor

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 Linux21d5be092d947f8d83f76f7ebf3989e7e9230a98Vendor (CNA)
Linux Linux352a278d5a1965aae3f817ce5d24a67ee42d45d1Vendor (CNA)
Linux Linux820871e9dbeecd2533c4c5f5d91878ceaf02324cVendor (CNA)
Linux Linux9646dfee880730aae4b379a4b8ee6c88ac735acdVendor (CNA)
Linux Linux989343b7ee5b1a08778be0c7c4bf6030d3910807Vendor (CNA)
Linux Linuxee611a7509554c4ca1f54f6aefe592fb1df7ea70Vendor (CNA)
debian:linux7.2.6-1 · Debian:14Package 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.

No dated events beyond publication.

EPSS, last 120 days+1% in 7 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.

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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

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

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. SSVC exploitation— → none
  2. Fix✗ → ✓

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

References

Show all references (5 more)

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

All records