GHSA-64C8-8QX9-25R7
Vulnerability from github – Published: 2026-06-02 18:31 – Updated: 2026-06-02 18:31CZ.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.
{
"affected": [],
"aliases": [
"CVE-2026-49943"
],
"database_specific": {
"cwe_ids": [
"CWE-121"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-02T17:16:37Z",
"severity": "MODERATE"
},
"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\u0027s position is that a fix is not being prioritized because all network operators should already be rejecting routes with unusually long attributes.",
"id": "GHSA-64c8-8qx9-25r7",
"modified": "2026-06-02T18:31:34Z",
"published": "2026-06-02T18:31:34Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-49943"
},
{
"type": "WEB",
"url": "https://bird.nic.cz"
},
{
"type": "WEB",
"url": "https://gitlab.nic.cz/labs/bird/-/blob/master/NEWS"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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