High [CVE-2026-89638] Linux kernel: Privilege escalation in SMB client due to improper handling of setuid/setgid bits
This high-severity Red Hat Linux advisory covers CVE-2026-89638.
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Summary
A flaw was found in the Linux kernel's Server Message Block (SMB) client. When a file with the setuid or setgid bit is written to on certain Common Internet File System (CIFS) mounts (specifically those using 'cifsacl', 'modefromsid' options, or SMB3.1.1 POSIX extensions), the kernel fails to properly clear these bits on the server.
This oversight allows the setuid/setgid bits to persist, which could enable a local attacker to achieve unexpected privilege escalation upon subsequent execution of the affected file. Red Hat severity: Moderate — CVSS 7.3 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:N).
Weakness: CWE-281.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 37 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 37 minutes ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 37 minutes ago·verify at source
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