CVE-2026-49943

EIP tracks 2 public exploits for CVE-2026-49943. PoCs published by cxwx, 9Bakabaka.

AI-analyzed exploit summary This PoC exploits a stack-based buffer overflow in BIRD Internet Routing Daemon's BGP AS_PATH mask matching implementation (CVE-2026-49943) by sending a crafted BGP UPDATE message with an excessively long AS_PATH (2295 ASNs), triggering a crash in the `as_path_match()` function.

CZ.NIC BIRD Internet Routing Daemon through 2.19.0 contains a stack-based buffer overflow in the BGP AS_PATH mask matching implementation in nest/a-path.c. The as_path_match() function uses a fixed-size stack array of 2048 + 1 pm_pos entries, while parse_path() expands AS_PATH segments from a received BGP UPDATE without enforcing a corresponding capacity limit. When RFC 8654 BGP Extended Messages are enabled and a BIRD filter evaluates an AS path mask expression such as "bgp_path ~ [= ... =]", an established BGP peer can send a long AS_PATH containing more than 2048 expanded ASNs. This causes parse_path()/as_path_match() to write beyond the fixed stack buffer, resulting in a crash of the daemon. NOTE: reportedly, the Supplier's position is that a fix is not being prioritized because all network operators should already be rejecting routes with unusually long attributes.