Kernel memory corruption via stale ksmbd callback
Published Jul 25, 2026 · Updated Jul 25, 2026
Use-after-free in ksmbd in Linux Kernel allows remote authenticated users to corrupt kernel memory via a crafted SMB request sequence. The CLOSED-work path frees a deferred file_lock but leaves its async request and smb2_remove_blocked_lock callback reachable, so a later SMB2_CANCEL dereferences the freed object. The sequence requires an authenticated SMB session, a blocked lock, SMB2_CLOSE on its handle, and a subsequent cancel for the same AsyncId.
Summary
What happened
Use-after-free in ksmbd in Linux Kernel allows remote authenticated users to corrupt kernel memory via a crafted SMB request sequence. The CLOSED-work path frees a deferred file_lock but leaves its async request and smb2_remove_blocked_lock callback reachable, so a later SMB2_CANCEL dereferences the freed object. The sequence requires an authenticated SMB session, a blocked lock, SMB2_CLOSE on its handle, and a subsequent cancel for the same AsyncId.
The record
- CVE
- CVE-2026-64437
- Published
- Jul 25, 2026
- Updated
- Jul 25, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- T1210
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 25, 2026CVE publishedPublication date reported by the CVE source.
- Jul 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
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Is a vulnerable build present?
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- Affected versionversion=0da2e073f9cbf4985a0fd9acb71bc5ff599f8afd <b8e274e69ab09222c7a552c7c0c1eef9ce627fc1
- Affected versionversion=14d2eee0193ac3cd1bf3d014373449f0b8d35d6d <94083db751930b1540ddff2b54d4677549c57f81
- Affected versionversion=2b2eda2821cff1d1b5a423b6ee7d8fc6fbc8e694
- Affected versionversion=6.1.176 <6.1.178
- Affected versionversion=6.12.94 <6.12.96
- Affected versionversion=6.18.36 <6.18.39
- Affected versionversion=6.6.143 <6.6.145
- Affected versionversion=7.0.13 <7.1
- Affected versionversion=7.1
- Affected versionversion=89ae9df09d2c1fb4a4eb495c113a7ce1dca34147 <ddb9239828336b36d8a3ef5943fdffb2f55b6508
- Affected versionversion=b7063c7426ea5a4d15e01b60538718765392f49d <a796ba4e61d5e14e07b79a359faac69f8f9b22a3
- Affected versionversion=f580d27e8928828693df44ba2db0fffdbe11dfea <10f293a07f9e10e988b0ae44e2e99c631f5a68e0
- Affected versionversion=f580d27e8928828693df44ba2db0fffdbe11dfea <12c36c99655f325befe50c26842f7deca414c381
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
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Technologies
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