CVE-2026-89655ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
- 9.8CriticalCVSS base score
- 0.71%Exploitation in 30 daysEPSS · top 46% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
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.
Timeline
ID reserved
By Linux
Published
- 38 days later
· 38 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Received | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.71% · top 46% of all CVEs (12 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.
Affected products
- affected e4500b5e35c213e0f97be7cb69328c0877203a79 – < 091137821e1fc88f37e15201abf055c9494ddc61
- affected e4500b5e35c213e0f97be7cb69328c0877203a79 – < 01542430081014d80fc9e70e92d6647432ddb7fc
- affected e4500b5e35c213e0f97be7cb69328c0877203a79 – < 23eb34a53a53cb1a6dab1eeee830633207ac158d
- affected e4500b5e35c213e0f97be7cb69328c0877203a79 – < 19f16f04c2b014a7dd214dc1e42557d8530b16f3
- affected e4500b5e35c213e0f97be7cb69328c0877203a79 – < 2701431aa3cc8b23efe6890182e7b04f5e76fab5
- affected e4500b5e35c213e0f97be7cb69328c0877203a79 – < fe46746087b5b9c5bb2d022df6c7819218494ced
- affected e4500b5e35c213e0f97be7cb69328c0877203a79 – < 2dba24dcd5050be4b7b119e6f0b01f62203b5d26
- affected e4500b5e35c213e0f97be7cb69328c0877203a79 – < 7af4c4f01305b0935adf6d4301b1ec407025485d
- affected 4.8
- unaffected < 4.8
- unaffected 5.10.270 – ≤ 5.10.*
- unaffected 5.15.221 – ≤ 5.15.*
- unaffected 6.1.188 – ≤ 6.1.*
- unaffected 6.6.157 – ≤ 6.6.*
- unaffected 6.12.109 – ≤ 6.12.*
- unaffected 6.18.50 – ≤ 6.18.*
- unaffected 7.2.4 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References8
- https://git.kernel.org/stable/c/091137821e1fc88f37e15201abf055c9494ddc61 (opens in a new tab)
- https://git.kernel.org/stable/c/01542430081014d80fc9e70e92d6647432ddb7fc (opens in a new tab)
- https://git.kernel.org/stable/c/23eb34a53a53cb1a6dab1eeee830633207ac158d (opens in a new tab)
- https://git.kernel.org/stable/c/19f16f04c2b014a7dd214dc1e42557d8530b16f3 (opens in a new tab)
- https://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5 (opens in a new tab)
- https://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced (opens in a new tab)
- https://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26 (opens in a new tab)
- https://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-76567 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://cveledger.app/cve/CVE-2026-89655)Record last updated .