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CVE-2026-49943

Estado: AplazadaMedia (6.3)—

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.

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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

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Cz.nic — BirdAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-49943",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-49943",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-06-02T18:20:11.710969Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "cve@mitre.org",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 6.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 4,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "NIC",
          "product": "BIRD",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "versionType": "semver",
              "lessThanOrEqual": "2.19.0"
            }
          ],
          "defaultStatus": "unknown"
        }
      ]
    }
  ],
  "published": "2026-06-02T17:16:37.657",
  "references": [
    {
      "url": "https://bird.nic.cz",
      "source": "cve@mitre.org"
    },
    {
      "url": "https://gitlab.nic.cz/labs/bird/-/blob/master/NEWS",
      "source": "cve@mitre.org"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "cve@mitre.org",
      "description": [
        {
          "lang": "en",
          "value": "CWE-121"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    },
    {
      "lang": "es",
      "value": "CZ.NIC BIRD Internet Routing Daemon hasta la versión 2.19.0 contiene un desbordamiento de búfer basado en pila en la implementación de coincidencia de máscara BGP AS_PATH en nest/a-path.c. La función as_path_match() utiliza un array de pila de tamaño fijo de 2048 + 1 entradas pm_pos, mientras que parse_path() expande segmentos AS_PATH de una ACTUALIZACIÓN BGP recibida sin aplicar un límite de capacidad correspondiente. Cuando los Mensajes Extendidos BGP RFC 8654 están habilitados y un filtro BIRD evalúa una expresión de máscara de ruta AS como 'bgp_path ~ [= ... =]', un par BGP establecido puede enviar una AS_PATH larga que contenga más de 2048 ASNs expandidos. Esto provoca que parse_path()/as_path_match() escriba más allá del búfer de pila fijo, lo que resulta en un fallo del demonio. NOTA: según se informa, la posición del Proveedor es que una solución no está siendo priorizada porque todos los operadores de red ya deberían estar rechazando rutas con atributos inusualmente largos."
    }
  ],
  "lastModified": "2026-07-22T19:10:00.120",
  "sourceIdentifier": "cve@mitre.org"
}