Signal Delivery Bypass in FreeBSD's Capsicum Implementation

CVE-2026-45259

What is CVE-2026-45259?

The implementation of the sigqueue(2) function in FreeBSD's Capsicum framework allows a process running in capability mode to send signals to other processes irresponsibly, circumventing intended restrictions. This vulnerability arises because the kern_sigqueue function neglects to verify if the signal delivery is confined to the calling process's own PID. As a result, a compromised process operating within a Capsicum sandbox could use this loophole to disrupt other processes by sending critical signals like SIGKILL or SIGSTOP. This scenario presents a significant risk, especially for processes run by the same user or superuser sandboxed processes, undermining the integrity and isolation that Capsicum aims to enforce.

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