{
  "affected": [
    {
      "affectedData": [
        {
          "product": "synapse",
          "vendor": "element-hq",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.138.3"
            },
            {
              "status": "affected",
              "version": "= 1.139.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Synapse is an open source Matrix homeserver implementation. Lack of validation for device keys in Synapse before 1.138.3 and in Synapse 1.139.0 allow an attacker registered on the victim homeserver to degrade federation functionality, unpredictably breaking outbound federation to other homeservers. The issue is patched in Synapse 1.138.3, 1.138.4, 1.139.1, and 1.139.2. Note that even though 1.138.3 and 1.139.1 fix the vulnerability, they inadvertently introduced an unrelated regression. For this reason, the maintainers of Synapse recommend skipping these releases and upgrading straight to 1.138.4 and 1.139.2."
    },
    {
      "lang": "es",
      "value": "Synapse es una implementaci\u00f3n de homeserver de Matrix de c\u00f3digo abierto. La falta de validaci\u00f3n para las claves de dispositivo en Synapse anterior a 1.138.3 y en Synapse 1.139.0 permite a un atacante registrado en el homeserver v\u00edctima degradar la funcionalidad de federaci\u00f3n, rompiendo impredeciblemente la federaci\u00f3n saliente a otros homeservers. El problema est\u00e1 parcheado en Synapse 1.138.3, 1.138.4, 1.139.1 y 1.139.2. Tenga en cuenta que aunque 1.138.3 y 1.139.1 solucionan la vulnerabilidad, introdujeron inadvertidamente una regresi\u00f3n no relacionada. Por esta raz\u00f3n, los mantenedores de Synapse recomiendan omitir estas versiones y actualizar directamente a 1.138.4 y 1.139.2."
    }
  ],
  "id": "CVE-2025-61672",
  "lastModified": "2026-10-08T13:10:00.200",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "LOW",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "LOW",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "LOW",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2025-61672",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2025-10-15T16:10:58.297046Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2025-10-08T15:16:25.110",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/element-hq/synapse/commit/26aaaf9e48fff80cf67a20c691c75d670034b3c1"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/element-hq/synapse/commit/7069636c2d6d1ef2022287addf3ed8b919ef2740"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/element-hq/synapse/pull/17097"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/element-hq/synapse/releases/tag/v1.138.3"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/element-hq/synapse/releases/tag/v1.139.1"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/element-hq/synapse/security/advisories/GHSA-fh66-fcv5-jjfr"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-1287"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}