Skip to content
Noroxi
NVD / CVE Program· CNA Linux

CVE-2026-89655: ceph: fix UAF in __kick_flushing_caps() on cf entry 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: 0.71% (FIRST EPSS); higher than 53.3% 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 01542430081014d80fc9e70e92d6647432ddb7fc, 091137821e1fc88f37e15201abf055c9494ddc61, 19f16f04c2b014a7dd214dc1e42557d8530b16f3.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 01542430081014d80fc9e70e92d6647432ddb7fc, 091137821e1fc88f37e15201abf055c9494ddc61, 19f16f04c2b014a7dd214dc1e42557d8530b16f3 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 __kick_flushing_caps() on cf entry freed during unlock list_for_each_entry() iterates ci->i_cap_flush_list but drops i_ceph_lock to send cap messages. During the unlock window, handle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries with tid <= flush_tid from the list, release i_ceph_lock, and free them via ceph_free_cap_flush() outside any lock. When the original thread reacquires i_ceph_lock and the for-loop macro advances via cf = list_next_entry(cf, i_list), it dereferences cf->i_list.next on freed memory. The race timeline: __kick_flushing_caps() handle_cap_flush_ack() ----------------------- ----------------------- holds i_ceph_lock <--- iterates to cf (tid=10) prepares FLUSH message drops i_ceph_lock <--- __send_cap() ── FLUSH(tid=10) MDS sends FLUSH_ACK(tid=10) ---> acquires i_ceph_lock cf->tid(10) <= flush_tid(10), detaches cf from i_cap_flush_list drops i_ceph_lock ceph_free_cap_flush(cf) <- frees it! acquires i_ceph_lock <--- for-loop advances: cf = list_next_entry(cf, i_list) -- UAF on freed cf->i_list.next The cf was just sent by __kick_flushing_caps itself via __send_cap(). The MDS may respond with FLUSH_ACK quickly enough that handle_cap_flush_ack() frees cf before __kick_flushing_caps can finish the iteration. Fix by converting to a manual while loop: save the next pointer under i_ceph_lock before dropping it, then use the saved pointer after reacquiring, so the potentially-freed cf is never accessed again.

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Sep 11, 2026
Updated
Oct 19, 2026
EPSS
0.7% · 53th 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 · 0.7%

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-2026-89655

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

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for linux records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

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.

We use this product, ask for help

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

    • 4.8affected
    • e4500b5e35c213e0f97be7cb69328c0877203a79 and later · before 091137821e1fc88f37e15201abf055c9494ddc61affected · git
    • e4500b5e35c213e0f97be7cb69328c0877203a79 and later · before 01542430081014d80fc9e70e92d6647432ddb7fcaffected · git
    • e4500b5e35c213e0f97be7cb69328c0877203a79 and later · before 23eb34a53a53cb1a6dab1eeee830633207ac158daffected · git
    • e4500b5e35c213e0f97be7cb69328c0877203a79 and later · before 19f16f04c2b014a7dd214dc1e42557d8530b16f3affected · git
    • e4500b5e35c213e0f97be7cb69328c0877203a79 and later · before 2701431aa3cc8b23efe6890182e7b04f5e76fab5affected · git
    • e4500b5e35c213e0f97be7cb69328c0877203a79 and later · before fe46746087b5b9c5bb2d022df6c7819218494cedaffected · git
    • e4500b5e35c213e0f97be7cb69328c0877203a79 and later · before 2dba24dcd5050be4b7b119e6f0b01f62203b5d26affected · git
    • e4500b5e35c213e0f97be7cb69328c0877203a79 and later · before 7af4c4f01305b0935adf6d4301b1ec407025485daffected · git
    • before 4.8not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.190-16.1.190-1
Debian:12linux-6.12before 6.12.111-1~deb12u16.12.111-1~deb12u1
Debian:13linuxbefore 6.12.111-16.12.111-1
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-2026-89653Sep 11, 2026 · ceph: reject export_targets ranks >= CEPH_MAX_MDS in mdsmap decode
    39Monitor
  • ← EarlierCVE-2026-89654Sep 11, 2026 · ceph: fix UAF in check_new_map() on session freed during unlock
    39Monitor
  • Later →CVE-2026-89656Sep 11, 2026 · libceph: reject buckets with mismatched CRUSH ids
    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 Linux01542430081014d80fc9e70e92d6647432ddb7fcVendor (CNA)
Linux Linux091137821e1fc88f37e15201abf055c9494ddc61Vendor (CNA)
Linux Linux19f16f04c2b014a7dd214dc1e42557d8530b16f3Vendor (CNA)
Linux Linux23eb34a53a53cb1a6dab1eeee830633207ac158dVendor (CNA)
Linux Linux2701431aa3cc8b23efe6890182e7b04f5e76fab5Vendor (CNA)
Linux Linux2dba24dcd5050be4b7b119e6f0b01f62203b5d26Vendor (CNA)
Linux Linux7af4c4f01305b0935adf6d4301b1ec407025485dVendor (CNA)
Linux Linuxfe46746087b5b9c5bb2d022df6c7819218494cedVendor (CNA)
debian:linux6.1.190-1 · Debian:12Package registry (OSV)
debian:linux6.12.111-1 · Debian:13Package registry (OSV)
debian:linux-6.126.12.111-1~deb12u1 · Debian:12Package 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.

—

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 (7 more)

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

All records