VulnerabilityDeferred

CVE-2026-49943

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.

MEDIUM 6.3EPSS 0.30%

Does this matter?

Lower severity and a low EPSS score (0.30%). Track it; it rarely justifies an emergency change on its own.

Description

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.

CVSS 3.1: 6.3 MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H
EPSS: 0.30% probability · 23th percentile
CISA KEV: Not listed
Weakness: CWE-121
Source: cve@mitre.org

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.