FreeBSD: unlinkat AT_RESOLVE_BENEATH flag dropped, path containment bypass
CVE-2026-49421 Published on August 19, 2026

unlinkat(2) ignores AT_RESOLVE_BENEATH flag
The kernel function that implements unlinkat(2) and funlinkat(2) validated the AT_RESOLVE_BENEATH flag but failed to pass it through to the underlying path lookup. The flag was silently dropped, so path resolution was not actually restricted. A process that uses AT_RESOLVE_BENEATH with unlinkat(2) or funlinkat(2) to confine path resolution can in fact resolve paths above the starting directory. A caller relying on this flag for path containment may delete files outside the intended directory tree.

Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-49421 can be exploited with local system access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, a high impact on integrity and availability.

Attack Vector:
LOCAL
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
HIGH
Availability Impact:
HIGH

Weakness Type

Improper Check for Dropped Privileges

The software attempts to drop privileges but does not check or incorrectly checks to see if the drop succeeded. If the drop fails, the software will continue to run with the raised privileges, which might provide additional access to unprivileged users.


Products Associated with CVE-2026-49421

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FreeBSD
 

Affected Versions

FreeBSD: