{"containers":{"cna":{"affected":[{"product":"synapse","vendor":"matrix-org","versions":[{"status":"affected","version":">=0.99.0, < 1.25.0"}]}],"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."}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":4.3,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","description":"CWE-400 Uncontrolled Resource Consumption","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2021-08-02T02:06:23.000Z","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M"},"references":[{"tags":["x_refsource_CONFIRM"],"url":"https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8"},{"tags":["x_refsource_MISC"],"url":"https://github.com/matrix-org/synapse/releases/tag/v1.25.0"},{"tags":["x_refsource_MISC"],"url":"https://github.com/matrix-org/synapse/pull/8950"},{"tags":["x_refsource_MISC"],"url":"https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6"},{"name":"FEDORA-2021-a627cfd31e","tags":["vendor-advisory","x_refsource_FEDORA"],"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/"}],"source":{"advisory":"GHSA-2hwx-mjrm-v3g8","discovery":"UNKNOWN"},"title":"Denial of service attack via .well-known lookups","x_legacyV4Record":{"CVE_data_meta":{"ASSIGNER":"security-advisories@github.com","ID":"CVE-2021-21274","STATE":"PUBLIC","TITLE":"Denial of service attack via .well-known lookups"},"affects":{"vendor":{"vendor_data":[{"product":{"product_data":[{"product_name":"synapse","version":{"version_data":[{"version_value":">=0.99.0, < 1.25.0"}]}}]},"vendor_name":"matrix-org"}]}},"data_format":"MITRE","data_type":"CVE","data_version":"4.0","description":{"description_data":[{"lang":"eng","value":"Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). 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