Out-of-bounds access via truncated SMB DACL
Published May 1, 2026 · Updated May 1, 2026
Out-of-bounds access in the Linux Kernel 5.12 SMB client allows remote attackers to trigger kernel memory access via a truncated DACL. build_sec_desc() and id_mode_to_cifs_acl() trust a server-supplied DACL header, and rewrite helpers walk ACEs without validating each entry against the DACL bounds. A Linux user must cause the client to process security-descriptor data from a malicious SMB server; the record does not specify whether the resulting access discloses data, corrupts memory, or crashes the system.
Summary
What happened
Out-of-bounds access in the Linux Kernel 5.12 SMB client allows remote attackers to trigger kernel memory access via a truncated DACL. build_sec_desc() and id_mode_to_cifs_acl() trust a server-supplied DACL header, and rewrite helpers walk ACEs without validating each entry against the DACL bounds. A Linux user must cause the client to process security-descriptor data from a malicious SMB server; the record does not specify whether the resulting access discloses data, corrupts memory, or crashes the system.
The record
- CVE
- CVE-2026-31709
- Published
- May 1, 2026
- Updated
- May 1, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- CWE-1288, T1203
- Attack vector
- network
- Privileges
- unauthenticated
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?
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- Affected versionversion=5.12
- Affected versionversion=bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 <0a8cf165566ba55a39fd0f4de172119dd646d39a
- Affected versionversion=bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 <b78db9bddc84136f6a0bb49e8883cf200dfb87a8
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
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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