FreeBSD Sigqueue Capability Check Flaw in Capsicum (CVE-2026-45259)
CVE-2026-45259 Published on June 27, 2026
sigqueue(2) missing capability mode restriction
sigqueue(2) was marked as permitted in capability mode with the introduction of Capsicum in 2011, but the implementation of kern_sigqueue did not include a capability mode check restricting signal delivery to the calling process's own PID.
A process in capability mode can use sigqueue(2) to send signals to any process it could signal following standard Unix permissions, bypassing the Capsicum sandbox restriction. A compromised sandboxed process could interfere with other processes, for example by sending SIGKILL or SIGSTOP. This could be any process running as the same user, or any process, for a superuser sandboxed process.
Vulnerability Analysis
CVE-2026-45259 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 and integrity, and a high impact on availability.
Weakness Type
Incorrect Privilege Assignment
A product incorrectly assigns a privilege to a particular actor, creating an unintended sphere of control for that actor.
Products Associated with CVE-2026-45259
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Affected Versions
FreeBSD:- Version 15.0-RELEASE and below p10 is affected.
- Version 14.4-RELEASE and below p6 is affected.
- Version 14.3-RELEASE and below p15 is affected.