{"id":"CVE-2021-29471","state":"PUBLISHED","title":"Denial of service in Matrix Synapse","description":"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 1.33.2 \"Push rules\" can specify conditions under which they will match, including `event_match`, which matches event content against a pattern including wildcards. Certain patterns can cause very poor performance in the matching engine, leading to a denial-of-service when processing moderate length events. The issue is patched in version 1.33.2. A potential workaround might be to prevent users from making custom push rules, by blocking such requests at a reverse-proxy.","publishedAt":"2021-05-11T15:05:12.000Z","updatedAt":"2024-08-03T22:11:05.476Z","severity":{"score":3.7,"label":"Low","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["matrix-org synapse"],"affected":[{"vendor":"matrix-org","product":"synapse","versions":[{"version":"< 1.33.2","status":"affected"}]}],"references":["https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85","https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c","https://github.com/matrix-org/synapse/releases/tag/v1.33.2","https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/"],"weaknesses":["CWE-400"],"ingestedAt":"2026-10-29T19:48:21.578Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/29xxx/CVE-2021-29471.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2021-29471","state":"PUBLISHED","datePublished":"2021-05-11T15:05:12.000Z","dateUpdated":"2024-08-03T22:11:05.476Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2021-03-30T00:00:00.000Z"},"containers":{"cna":{"title":"Denial of service in Matrix Synapse","descriptions":[{"lang":"en","value":"Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). 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