CVE-2026-64396ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation
- 8.8HighCVSS base score
- 0.43%Exploitation in 30 daysEPSS · top 62% 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: ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation When a blocking byte-range lock request is deferred in the FILE_LOCK_DEFERRED path, ksmbd registers the asynchronous work into the connection's async_requests list via setup_async_work(). The cancel callback smb2_remove_blocked_lock() holds a reference to the flock. If the lock waiter is subsequently woken up but the work state is no longer KSMBD_WORK_ACTIVE (e.g., due to a concurrent cancellation), the cleanup path calls locks_free_lock(flock) without dequeuing the work from the async_requests list. Concurrently, smb2_cancel() walks the list under conn->request_lock and invokes the cancel callback, which then dereferences the already freed 'flock'. This leads to a slab-use-after-free inside __wake_up_common. Fix this by restructuring the cleanup logic after the worker returns from ksmbd_vfs_posix_lock_wait(). Move list_del(&smb_lock->llist) and release_async_work(work) to the top of the cleanup block. This guarantees that the async work is completely dequeued and serialized under conn->request_lock before locks_free_lock(flock) is called, rendering the flock unreachable for any concurrent smb2_cancel().
Timeline
ID reserved
By Linux
- 6 days later
· 6 days later
Published
- 23 days later
· 23 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 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Analyzed | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.43% · top 62% of all CVEs (12 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.8.
Affected products
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < 367c42a611fe488b7b03f1f6737f4dee0e8b20a2
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < 7703fd9aba1f2483c8e55f9ff73b7663e0761ed9
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < 463bbd79698513af4dad50fe1c573825f297ca2e
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < 5aa1cb01155f96824003baf7997cdf1f150caba3
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < 5c75275c0fc9a2deb0d8f5604edcb16f288171c8
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e
- affected 5.15
- unaffected < 5.15
- unaffected 6.1.178 – ≤ 6.1.*
- unaffected 6.6.145 – ≤ 6.6.*
- unaffected 6.12.96 – ≤ 6.12.*
- unaffected 6.18.39 – ≤ 6.18.*
- unaffected 7.1.4 – ≤ 7.1.*
- unaffected 7.2 – ≤ *
References
References6
- https://git.kernel.org/stable/c/367c42a611fe488b7b03f1f6737f4dee0e8b20a2 (opens in a new tab)
- https://git.kernel.org/stable/c/7703fd9aba1f2483c8e55f9ff73b7663e0761ed9 (opens in a new tab)
- https://git.kernel.org/stable/c/463bbd79698513af4dad50fe1c573825f297ca2e (opens in a new tab)
- https://git.kernel.org/stable/c/5aa1cb01155f96824003baf7997cdf1f150caba3 (opens in a new tab)
- https://git.kernel.org/stable/c/5c75275c0fc9a2deb0d8f5604edcb16f288171c8 (opens in a new tab)
- https://git.kernel.org/stable/c/d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e (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-2026-48940 (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)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-64396)Record last updated .