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. 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.

Published: 2026-06-02 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Deferred，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-49943 is rated Low Risk (33/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.30%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-49943

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.04% 0.30% +0.26%
2 2026-06-03 — 0.04% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-49943

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 4.0 [email protected]

Weakness enumeration for CVE-2026-49943

GitHub Security Advisory for CVE-2026-49943

GHSA-64c8-8qx9-25r7 · Severity: medium — CZ.NIC BIRD Internet Routing Daemon through 2.19.0 contains a stack-based buffer overflow in the...

OS Trackers for CVE-2026-49943

vendor priority summary link
debian unimportant CVE-2026-49943 unimportant priority: Debian including 3 source packages (bird, bird2, bird3), 10 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 10. https://security-tracker.debian.org/tracker/CVE-2026-49943
ubuntu medium CVE-2026-49943 medium priority: Ubuntu including 3 source packages (bird, bird2, bird3), 18 status rows across 7 suites (bionic, focal, jammy, noble, questing, resolute, upstream): needs-triage 14, DNE 4. https://ubuntu.com/security/CVE-2026-49943

Affected software / configurations for CVE-2026-49943

Vendor Product Version Raw CPE
nic bird <= 2.19.0 cpe:2.3:a:nic:bird:*:*:*:*:*:*:*:*

References for CVE-2026-49943

cvelogic Threat Intelligence