{"resultsPerPage":1,"startIndex":0,"totalResults":1,"format":"NVD_CVE","version":"2.0","timestamp":"2026-05-16T23:09:51.164","vulnerabilities":[{"cve":{"id":"CVE-2021-21274","sourceIdentifier":"security-advisories@github.com","published":"2021-02-26T18:15:12.237","lastModified":"2024-11-21T05:47:54.520","vulnStatus":"Modified","cveTags":[],"descriptions":[{"lang":"en","value":"Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.25.0, a malicious homeserver could redirect requests to their .well-known file to a large file. This can lead to a denial of service attack where homeservers will consume significantly more resources when requesting the .well-known file of a malicious homeserver. This affects any server which accepts federation requests from untrusted servers. Issue is resolved in version 1.25.0. As a workaround the `federation_domain_whitelist` setting can be used to restrict the homeservers communicated with over federation."},{"lang":"es","value":"Synapse es un servidor doméstico de referencia de Matrix escrito en python (paquete pypi matrix-synapse). Matrix es un ecosistema para VoIP y mensajería instantánea federada abierta. En Synapse versiones anteriores a 1.25.0, un servidor doméstico malicioso podía redireccionar las peticiones para su archivo .well-known a un archivo grande. Esto puede conllevar a un ataque de denegación de servicio en el que los servidores domésticos consumirán significativamente más recursos al solicitar el archivo .well-known de un servidor doméstico malicioso. Esto afecta a cualquier servidor que acepte peticiones de federación desde servidores que no sean confiables. El problema es resuelto en versión 1.25.0. Como solución alternativa, el ajuste de \"federation_domain_whitelist\" puede ser usado para restringir los servidores domésticos que se comunican con la federación"}],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","baseScore":4.3,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW"},"exploitabilityScore":2.8,"impactScore":1.4},{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","baseScore":6.5,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":3.6}],"cvssMetricV2":[{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"2.0","vectorString":"AV:N/AC:M/Au:N/C:N/I:N/A:P","baseScore":4.3,"accessVector":"NETWORK","accessComplexity":"MEDIUM","authentication":"NONE","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"PARTIAL"},"baseSeverity":"MEDIUM","exploitabilityScore":8.6,"impactScore":2.9,"acInsufInfo":false,"obtainAllPrivilege":false,"obtainUserPrivilege":false,"obtainOtherPrivilege":false,"userInteractionRequired":true}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Secondary","description":[{"lang":"en","value":"CWE-400"}]},{"source":"nvd@nist.gov","type":"Primary","description":[{"lang":"en","value":"CWE-770"}]}],"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*","versionStartIncluding":"0.99.0","versionEndExcluding":"1.25.0","matchCriteriaId":"6C16EE11-380E-400F-9A55-6068AAF132D8"}]}]},{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*","matchCriteriaId":"A930E247-0B43-43CB-98FF-6CE7B8189835"}]}]}],"references":[{"url":"https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6","source":"security-advisories@github.com","tags":["Patch","Third Party Advisory"]},{"url":"https://github.com/matrix-org/synapse/pull/8950","source":"security-advisories@github.com","tags":["Patch","Third Party Advisory"]},{"url":"https://github.com/matrix-org/synapse/releases/tag/v1.25.0","source":"security-advisories@github.com","tags":["Third Party Advisory"]},{"url":"https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8","source":"security-advisories@github.com","tags":["Patch","Third Party Advisory"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/","source":"security-advisories@github.com"},{"url":"https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6","source":"af854a3a-2127-422b-91ae-364da2661108","tags":["Patch","Third Party Advisory"]},{"url":"https://github.com/matrix-org/synapse/pull/8950","source":"af854a3a-2127-422b-91ae-364da2661108","tags":["Patch","Third Party Advisory"]},{"url":"https://github.com/matrix-org/synapse/releases/tag/v1.25.0","source":"af854a3a-2127-422b-91ae-364da2661108","tags":["Third Party Advisory"]},{"url":"https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8","source":"af854a3a-2127-422b-91ae-364da2661108","tags":["Patch","Third Party Advisory"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/","source":"af854a3a-2127-422b-91ae-364da2661108"}]}}]}