CVE-2026-55996

{
  "id": "CVE-2026-55996",
  "sourceIdentifier": "[email protected]",
  "published": "2026-08-05T08:16:34.173",
  "lastModified": "2026-10-24T16:10:00.153",
  "vulnStatus": "Awaiting Analysis",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "A denial-of-service vulnerability was identified in multiple TLS listeners in Rancher. Both the cattle-cluster-agent component running in downstream clusters and the Rancher server itself use the dynamiclistener library to serve TLS traffic. Without an effective CN filter configured, dynamiclistener automatically appended to each serving certificate any hostname presented via Server Name Indication (SNI) in incoming TLS requests.\n\n\n\nAn unauthenticated attacker with network access within the affected cluster could send a large number of TLS requests with distinct hostnames, causing the serving certificate to accumulate an unbounded number of Subject Alternative Names (SANs). Eventually, the certificate grows large enough that TLS handshakes fail with an excessive message size error, causing a denial of service on the affected listeners."
    },
    {
      "lang": "es",
      "value": "Una vulnerabilidad de denegación de servicio fue identificada en múltiples oyentes TLS en Rancher. Tanto el componente cattle-cluster-agent ejecutándose en clústeres descendentes como el propio servidor de Rancher utilizan la biblioteca dynamiclistener para servir tráfico TLS. Sin un filtro CN efectivo configurado, dynamiclistener añadió automáticamente a cada certificado de servicio cualquier nombre de host presentado a través de Server Name Indication (SNI) en las solicitudes TLS entrantes.\n\nUn atacante no autenticado con acceso de red dentro del clúster afectado podría enviar un gran número de solicitudes TLS con nombres de host distintos, haciendo que el certificado de servicio acumule un número ilimitado de Subject Alternative Names (SANs). Finalmente, el certificado crece lo suficiente como para que los handshakes TLS fallen con un error de tamaño de mensaje excesivo, causando una denegación de servicio en los oyentes afectados."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "SUSE",
          "product": "Rancher",
          "defaultStatus": "unaffected",
          "packageName": "Rancher",
          "versions": [
            {
              "version": "2.11.0",
              "lessThan": "2.11.16",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "2.12.0",
              "lessThan": "2.12.12",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "2.13.0",
              "lessThan": "2.13.8",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "2.14.0",
              "lessThan": "2.14.4",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
          "baseScore": 4.3,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "LOW"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 1.4
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-08-05T13:40:18.178968Z",
          "id": "CVE-2026-55996",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://bugzilla.suse.com/show_bug.cgi?id=CVE-2026-55996",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/rancher/rancher/security/advisories/GHSA-9jxv-832x-45q9",
      "source": "[email protected]"
    }
  ]
}