In the Linux kernel, the following vulnerability has been resolved: smb: client: harden POSIX SID length parsing posix_info_sid_size() reads sid[1]… (CVE-2026-64380)
A vulnerability in the Linux kernel's SMB client component related to POSIX SID length parsing has been resolved. The function posix_info_sid_size() improperly reads sid[1] to obtain the subauthority count with insufficient boundary checks, allowing buffers with only one remaining byte to be accepted. The fix requires two bytes before reading sid[1], preventing truncated POSIX SIDs from being processed unsafely.
AI Analysis
Technical Summary
The Linux kernel SMB client had a vulnerability in the posix_info_sid_size() function where it read the second byte (sid[1]) to determine the subauthority count without adequate boundary checking. The existing check allowed buffers with only one remaining byte, which could lead to unsafe processing of truncated POSIX SIDs. The vulnerability was resolved by requiring at least two bytes before reading sid[1], ensuring that all client code paths that use this helper reject truncated POSIX SIDs safely.
Potential Impact
This vulnerability could have allowed improper handling of truncated POSIX SIDs in the SMB client, potentially leading to memory safety issues such as out-of-bounds reads. No known exploits in the wild have been reported. The exact impact on confidentiality, integrity, or availability is not detailed in the provided information.
Mitigation Recommendations
A fix has been implemented in the Linux kernel to harden the POSIX SID length parsing by requiring two bytes before reading sid[1]. Users should update to the fixed Linux kernel version once available. Patch status is not explicitly confirmed in the provided data; check the vendor advisory for current remediation guidance.
In the Linux kernel, the following vulnerability has been resolved: smb: client: harden POSIX SID length parsing posix_info_sid_size() reads sid[1]… (CVE-2026-64380)
Description
A vulnerability in the Linux kernel's SMB client component related to POSIX SID length parsing has been resolved. The function posix_info_sid_size() improperly reads sid[1] to obtain the subauthority count with insufficient boundary checks, allowing buffers with only one remaining byte to be accepted. The fix requires two bytes before reading sid[1], preventing truncated POSIX SIDs from being processed unsafely.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel SMB client had a vulnerability in the posix_info_sid_size() function where it read the second byte (sid[1]) to determine the subauthority count without adequate boundary checking. The existing check allowed buffers with only one remaining byte, which could lead to unsafe processing of truncated POSIX SIDs. The vulnerability was resolved by requiring at least two bytes before reading sid[1], ensuring that all client code paths that use this helper reject truncated POSIX SIDs safely.
Potential Impact
This vulnerability could have allowed improper handling of truncated POSIX SIDs in the SMB client, potentially leading to memory safety issues such as out-of-bounds reads. No known exploits in the wild have been reported. The exact impact on confidentiality, integrity, or availability is not detailed in the provided information.
Mitigation Recommendations
A fix has been implemented in the Linux kernel to harden the POSIX SID length parsing by requiring two bytes before reading sid[1]. Users should update to the fixed Linux kernel version once available. Patch status is not explicitly confirmed in the provided data; check the vendor advisory for current remediation guidance.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-86gc-pxpc-4p5h
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-64380"]
- Ecosystems
- []
- Database Specific Severity
- null
- Cvss Version
- null
Threat ID: 6a65420b9c2644c7f8084a53
Added to database: 07/25/2026, 23:08:59 UTC
Last enriched: 07/25/2026, 23:29:53 UTC
Last updated: 07/26/2026, 03:59:03 UTC
Views: 4
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