CVE-2026-45259
Received Received - Intake

sigqueue(2) Signal Delivery Bypass in FreeBSD

Publication date: 2026-06-27

Last updated on: 2026-06-27

Assigner: FreeBSD

Description
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.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-06-27
Last Modified
2026-06-27
Generated
2026-06-27
AI Q&A
2026-06-27
EPSS Evaluated
N/A
NVD
CVE-2026-45259
EUVD
EUVD-2026-39963

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
freebsd freebsd *

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-266 A product incorrectly assigns a privilege to a particular actor, creating an unintended sphere of control for that actor.

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

CVE-2026-45259 is a vulnerability in FreeBSD's Capsicum sandbox framework related to the sigqueue(2) system call.

The problem is that sigqueue(2) was allowed in capability mode without proper restrictions, meaning a sandboxed process could send signals to any process it has permission to signal under standard Unix rules.

This bypasses the Capsicum sandbox restrictions, allowing a compromised sandboxed process to interfere with other processes by sending signals like SIGKILL or SIGSTOP.

This can affect any process running as the same user, or any process if the sandboxed process runs as a superuser.

Impact Analysis

This vulnerability allows a sandboxed process to bypass Capsicum restrictions and send signals to other processes it normally could not affect.

An attacker who compromises a sandboxed process could disrupt or terminate other processes by sending signals such as SIGKILL or SIGSTOP.

If the sandboxed process runs with superuser privileges, it could potentially interfere with any process on the system.

Mitigation Strategies

To mitigate CVE-2026-45259, you should upgrade your FreeBSD system to the corrected version that includes the patch for this vulnerability.

The update can be applied using pkg, freebsd-update, or by applying source code patches followed by recompiling the kernel.

After applying the update and recompiling the kernel, a system reboot is required to ensure the fix is active.

No workaround is available, so applying the official patch and rebooting is the only effective immediate step.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-45259. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart