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. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

A heap out-of-bounds write vulnerability exists in libevent prior to versions 2.1.13 and 2.2.2-alpha. The flaw is located in bufferevent_sock.c, where bufferevent_socket_set_conn_address_ improperly copies a kernel-supplied AF_UNIX peer address into a smaller fixed-size field. Release builds compiled with NDEBUG disable the EVUTIL_ASSERT length guard, allowing the evhttp accept path to pass a 110-byte sockaddr into a 28-byte field. An unauthenticated local attacker who can connect to an AF_UNIX listener can exploit this to overwrite adjacent heap data including the dns_request pointer. This leads to memory corruption with potential confidentiality, integrity, and availability impact. The vulnerability has been patched in libevent versions 2.1.13 and 2.2.2-alpha.