CVE-2026-64437ksmbd: fix use-after-free of a deferred file_lock on SMB2_CLOSE then SMB2_CANCEL
- 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 use-after-free of a deferred file_lock on SMB2_CLOSE then SMB2_CANCEL Commit f580d27e8928 ("ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL") made smb2_cancel() skip a work whose state is KSMBD_WORK_CANCELLED, so its cancel_fn cannot be fired a second time. But KSMBD_WORK has three states (ACTIVE, CANCELLED, CLOSED), and the same freeing producer path is reached for CLOSED too: SMB2_CLOSE on the locking handle -> set_close_state_blocked_works() sets the deferred work's state to KSMBD_WORK_CLOSED and wakes the smb2_lock() worker. The worker takes the non-ACTIVE early-exit, locks_free_lock()s the file_lock and, because the state is not KSMBD_WORK_CANCELLED, takes the STATUS_RANGE_NOT_LOCKED branch with "goto out2" -- which, like the cancelled branch, skips release_async_work(). The work stays on conn->async_requests with a live cancel_fn = smb2_remove_blocked_lock pointing at the freed file_lock. A subsequent SMB2_CANCEL for the same AsyncId then passes the KSMBD_WORK_CANCELLED-only guard (its state is KSMBD_WORK_CLOSED), so smb2_cancel() fires cancel_fn again over the freed file_lock -- the same use-after-free fixed, via SMB2_CLOSE instead of a first SMB2_CANCEL: BUG: KASAN: slab-use-after-free in __locks_delete_block __locks_delete_block locks_delete_block ksmbd_vfs_posix_lock_unblock smb2_remove_blocked_lock smb2_cancel <- 2nd SMB2_CANCEL fires cancel_fn handle_ksmbd_work Allocated by ...: locks_alloc_lock <- smb2_lock Freed by ...: locks_free_lock <- smb2_lock (non-ACTIVE early-exit) ... cache file_lock_cache of size 192 Reproduced on mainline 7.1-rc7 (which already contains f580d27e8928) with KASAN by an authenticated SMB client; the double-SMB2_CANCEL control is silent on that kernel, so the splat is attributable to the CLOSE trigger. Only an ACTIVE deferred work may have its cancel_fn fired: both terminal states (CANCELLED and CLOSED) reach the smb2_lock() early-exit that frees the file_lock and skips release_async_work(). Guard on KSMBD_WORK_ACTIVE so any non-active work is skipped.
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 (14 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 b7063c7426ea5a4d15e01b60538718765392f49d – < a796ba4e61d5e14e07b79a359faac69f8f9b22a3
- affected 0da2e073f9cbf4985a0fd9acb71bc5ff599f8afd – < b8e274e69ab09222c7a552c7c0c1eef9ce627fc1
- affected 89ae9df09d2c1fb4a4eb495c113a7ce1dca34147 – < ddb9239828336b36d8a3ef5943fdffb2f55b6508
- affected 14d2eee0193ac3cd1bf3d014373449f0b8d35d6d – < 94083db751930b1540ddff2b54d4677549c57f81
- affected f580d27e8928828693df44ba2db0fffdbe11dfea – < 12c36c99655f325befe50c26842f7deca414c381
- affected f580d27e8928828693df44ba2db0fffdbe11dfea – < 10f293a07f9e10e988b0ae44e2e99c631f5a68e0
- affected 2b2eda2821cff1d1b5a423b6ee7d8fc6fbc8e694
- affected 6.1.176 – < 6.1.178
- affected 6.6.143 – < 6.6.145
- affected 6.12.94 – < 6.12.96
- affected 6.18.36 – < 6.18.39
- affected 7.0.13 – < 7.1
- affected 7.1
- unaffected < 7.1
- 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/a796ba4e61d5e14e07b79a359faac69f8f9b22a3 (opens in a new tab)
- https://git.kernel.org/stable/c/b8e274e69ab09222c7a552c7c0c1eef9ce627fc1 (opens in a new tab)
- https://git.kernel.org/stable/c/ddb9239828336b36d8a3ef5943fdffb2f55b6508 (opens in a new tab)
- https://git.kernel.org/stable/c/94083db751930b1540ddff2b54d4677549c57f81 (opens in a new tab)
- https://git.kernel.org/stable/c/12c36c99655f325befe50c26842f7deca414c381 (opens in a new tab)
- https://git.kernel.org/stable/c/10f293a07f9e10e988b0ae44e2e99c631f5a68e0 (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-2026-48781 (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-2026-64437)Record last updated .