CVE-2026-49943CZ.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.
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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
- 6.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H
- Weakness (CWE)
- CWE-121
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- mitre
- NVD analysis
- Deferred
- Record last updated
- Jun 2, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
The CVE record on cve.org NVD's entry
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