CVE-2025-61920

{
  "id": "CVE-2025-61920",
  "sourceIdentifier": "[email protected]",
  "published": "2025-10-10T20:15:37.893",
  "lastModified": "2026-10-19T16:10:00.260",
  "vulnStatus": "Modified",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.5, Authlib’s JOSE implementation accepts unbounded JWS/JWT header and signature segments. A remote attacker can craft a token whose base64url‑encoded header or signature spans hundreds of megabytes. During verification, Authlib decodes and parses the full input before it is rejected, driving CPU and memory consumption to hostile levels and enabling denial of service. Version 1.6.5 patches the issue. Some temporary workarounds are available. Enforce input size limits before handing tokens to Authlib and/or use application-level throttling to reduce amplification risk."
    },
    {
      "lang": "es",
      "value": "Authlib es una biblioteca de Python que construye servidores OAuth y OpenID Connect. Antes de la versión 1.6.5, la implementación JOSE de Authlib acepta segmentos de encabezado y firma JWS/JWT ilimitados. Un atacante remoto puede crear un token cuyo encabezado o firma codificados en base64url abarca cientos de megabytes. Durante la verificación, Authlib decodifica y analiza la entrada completa antes de que sea rechazada, llevando el consumo de CPU y memoria a niveles hostiles y permitiendo la denegación de servicio. La versión 1.6.5 corrige el problema. Algunas soluciones temporales están disponibles. Imponga límites de tamaño de entrada antes de entregar tokens a Authlib y/o use la limitación a nivel de aplicación para reducir el riesgo de amplificación."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "authlib",
          "product": "authlib",
          "versions": [
            {
              "version": "< 1.6.5",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2025-10-10T20:46:55.883426Z",
          "id": "CVE-2025-61920",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        },
        {
          "lang": "en",
          "value": "CWE-400"
        },
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:*",
              "versionEndExcluding": "1.6.5",
              "matchCriteriaId": "B4367901-9190-47A3-88FA-173EE7C2FB13"
            }
          ]
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/authlib/authlib/commit/867e3f87b072347a1ae9cf6983cc8bbf88447e5e",
      "source": "[email protected]",
      "tags": [
        "Patch"
      ]
    },
    {
      "url": "https://github.com/authlib/authlib/security/advisories/GHSA-pq5p-34cr-23v9",
      "source": "[email protected]",
      "tags": [
        "Exploit",
        "Mitigation",
        "Vendor Advisory"
      ]
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00032.html",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ]
}