CVE-2026-49420: Buffer overflow in libalias RTSP handler
The RTSP handler in libalias rewrote outgoing packets into a fixed-length stack buffer without checking whether the rewritten data fit in the buffer, or whether the result fit back in the original packet.
A host sending crafted RTSP traffic from inside a NAT gateway using libalias can overflow a stack buffer, potentially achieving remote code execution in the kernel (when using ipfw(4) NAT) or in the natd(8) process (which generally runs as the root user).
Affected Software
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Systems using libalias to process RTSP traffic are exposed. The impact is in the kernel when libalias is used through ipfw(4) NAT, or in the natd(8) process when that service is used.
What does an attacker need to exploit it?
An attacker needs to send crafted RTSP traffic from inside a NAT gateway that uses libalias. The vulnerable code is reached when the RTSP handler rewrites outgoing packets.
What is the potential execution context if exploitation succeeds?
With ipfw(4) NAT, successful exploitation may result in remote code execution in the kernel. With natd(8), code execution may occur in the natd process, which generally runs as root.