Authenticated cross-user file access via unchecked durable-handle owner
Published May 1, 2026 · Updated May 1, 2026
Authorization bypass in the Linux Kernel allows remote authenticated users to hijack another user's orphaned ksmbd durable handle. SMB2_CREATE DHnC reconnects use an attacker-supplied persistent ID without matching the requester's security context to the stored opener. An authenticated SMB session, an orphaned handle, and enabled durable handles are required; the hijacked handle can read, alter, or delete files with the opener's rights.
Summary
What happened
Authorization bypass in the Linux Kernel allows remote authenticated users to hijack another user's orphaned ksmbd durable handle. SMB2_CREATE DHnC reconnects use an attacker-supplied persistent ID without matching the requester's security context to the stored opener. An authenticated SMB session, an orphaned handle, and enabled durable handles are required; the hijacked handle can read, alter, or delete files with the opener's rights.
The record
- CVE
- CVE-2026-31717
- Published
- May 1, 2026
- Updated
- May 1, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- T1005
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- May 1, 2026CVE publishedPublication date reported by the CVE source.
- May 1, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=6.9
- Affected versionversion=8df4bcdb0a4232192b2445256c39b787d58ef14d
- Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <00ce8d6789dae72d042a4522264964c72891ca37
- Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <49110a8ce654bbe56bef7c5e44cce31f4b102b8a
- Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <c908c853f304a4969b5aa10eba0b50350cc65b80
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- ksmbrace CVE-2026-31717 ACL-bypass PoCproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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