Use-After-Free Vulnerability in FreeBSD Kernel IPV6 Multicast Filter Handling

CVE-2026-49412

What is CVE-2026-49412?

A vulnerability in the FreeBSD kernel's handling of IPV6 multicast filters could allow an unprivileged local user to exploit a use-after-free condition. This issue arises when the kernel handler for IPV6_MSFILTER drops a serializing lock during the process of copying the source-filter list from userspace and later reacquires it. In this brief window, another thread may free the multicast filter structure, which leads to a stale pointer to previously freed memory being used by the handler. Successful exploitation of this vulnerability could allow an attacker to escalate their privileges within the system.

References