{"id":"UBUNTU-CVE-2021-29471","details":"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.","modified":"2025-10-24T04:50:16Z","published":"2021-05-11T15:15:00Z","upstream":["CVE-2021-29471"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-29471"},{"type":"REPORT","url":"https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85"},{"type":"REPORT","url":"https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c"},{"type":"REPORT","url":"https://github.com/matrix-org/synapse/releases/tag/v1.33.2"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2021-29471"}],"affected":[{"package":{"name":"matrix-synapse","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/matrix-synapse@0.24.0+dfsg-1ubuntu0.1~esm4?arch=source&distro=esm-apps/bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.19.2+dfsg-6","0.24.0+dfsg-1","0.24.0+dfsg-1ubuntu0.1~esm1","0.24.0+dfsg-1ubuntu0.1~esm4"],"ecosystem_specific":{"binaries":[{"binary_name":"matrix-synapse","binary_version":"0.24.0+dfsg-1ubuntu0.1~esm4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-29471.json"}},{"package":{"name":"matrix-synapse","ecosystem":"Ubuntu:Pro:20.04:LTS","purl":"pkg:deb/ubuntu/matrix-synapse@1.11.0-1ubuntu0.1~esm2?arch=source&distro=esm-apps/focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.3.0-1","1.4.0-1","1.5.0-1","1.5.1-1","1.6.0-1","1.6.1-1","1.7.0-2","1.7.1-1","1.7.2-1","1.7.3-1","1.8.0-1","1.9.0-1","1.9.1-1","1.10.0-1","1.10.0-2","1.11.0-1","1.11.0-1ubuntu0.1~esm2"],"ecosystem_specific":{"binaries":[{"binary_version":"1.11.0-1ubuntu0.1~esm2","binary_name":"matrix-synapse"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-29471.json"}},{"package":{"name":"matrix-synapse","ecosystem":"Ubuntu:Pro:22.04:LTS","purl":"pkg:deb/ubuntu/matrix-synapse@1.53.0-1ubuntu0.1~esm2?arch=source&distro=esm-apps/jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.39.0-1","1.47.0-2","1.47.1-1","1.48.0-1","1.49.0-1","1.49.2-1","1.50.1-1","1.50.2-1","1.51.0-1","1.52.0-1","1.53.0-1","1.53.0-1ubuntu0.1~esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"matrix-synapse","binary_version":"1.53.0-1ubuntu0.1~esm2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-29471.json"}}],"schema_version":"1.7.3","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},{"type":"Ubuntu","score":"medium"}]}