Bug 2484046 (CVE-2026-49943)

Summary: CVE-2026-49943 bird: BIRD Internet Routing Daemon: Denial of Service via stack-based buffer overflow in BGP AS_PATH processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: adudiak, kshier, stcannon, teagle, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the BIRD Internet Routing Daemon. An established BGP (Border Gateway Protocol) peer can send a specially crafted BGP UPDATE message containing an unusually long AS_PATH (Autonomous System Path) attribute. When a BIRD filter evaluates an AS path mask expression, this can lead to a stack-based buffer overflow in the `as_path_match()` function. This vulnerability can cause the daemon to crash, resulting in a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 2489778, 2489779    
Bug Blocks:    

Description OSIDB Bzimport 2026-06-02 18:01:43 UTC 
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.