High [CVE-2026-63388] Arbitrary code execution via heap out-of-bounds write in AF_UNIX handling

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has a heap out-of-bounds write in bufferevent_sock.c when bufferevent_socket_set_conn_address_ copies a kernel-supplied AF_UNIX peer address into bufferevent_private.conn_address.

Release builds compiled with NDEBUG disable the EVUTIL_ASSERT length guard, and the evhttp accept path can pass a 110-byte sockaddr from accept() into the 28-byte field.

An unauthenticated local peer able to connect to an AF_UNIX listener can overwrite the adjacent dns_request pointer and heap data, causing memory corruption with confidentiality, integrity, and availability impact. A flaw was found in Libevent.

A heap out-of-bounds write vulnerability in the `bufferevent_socket_set_conn_address_` function allows an unauthenticated local peer to achieve arbitrary code execution. By connecting to an AF_UNIX listener, an attacker can overwrite critical heap data, leading to memory corruption and potentially full control over the affected system.

By connecting to an AF_UNIX listener, an attacker can trigger a heap out-of-bounds write, leading to memory corruption and high impact on system confidentiality, integrity, and availability. The local attack vector limits the immediate threat, but the unauthenticated nature and severe consequences elevate its importance.