{"id":"CVE-2026-49943","details":"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.","modified":"2026-07-08T08:13:41.671038792Z","published":"2026-06-02T16:16:52.033Z","database_specific":{"cwe_ids":["CWE-121"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49943.json","cna_assigner":"mitre"},"references":[{"type":"WEB","url":"https://bird.nic.cz"},{"type":"WEB","url":"https://gitlab.nic.cz/labs/bird/-/blob/master/NEWS"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49943.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49943"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://gitlab.nic.cz/labs/bird","events":[{"introduced":"0"},{"fixed":"b82055f08f34ce99f17a9dac938e2359192727ab"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"last_affected":"2.19.0"},{"fixed":"2.19.0"}],"source":["AFFECTED_FIELD","DESCRIPTION"]}}],"versions":["v2.18","v2.17.1","v2.17","v2.16","v2.15","v2.15.1","v2.14","v2.13","v2.0.12","v2.0.11","v2.0.9","v2.0.8","v2.0.7","v2.0.6","v2.0.5","v2.0.4","v2.0.3","v2.0.2","v2.0.1","v2.0.0","v2.0.0-pre1","v2.0.0-pre0","v1.5.0","v1.4.5","v1.4.4","v1.4.2","v1.4.0","v1.4.1","v1.3.11","v1.3.10","v1.3.9","v1.3.8","v1.3.6","v1.3.5","v1.3.4","v1.3.3","v1.3.2","v1.3.1","v1.2.3","v1.2.2","v1.2.1","v1.2.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-49943.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H"}]}