{"schema_version":"1.7.5","id":"CVE-2021-29471","published":"2021-05-11T15:15:08.507Z","modified":"2026-07-08T06:27:13.881281978Z","aliases":["GHSA-x345-32rc-8h85","PYSEC-2021-135"],"related":["openSUSE-SU-2024:11041-1"],"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.","affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/matrix-org/synapse","events":[{"introduced":"0"},{"fixed":"d1473f7362e9b146dbd256076c8e3c7d163e7d94"},{"fixed":"03318a766cac9f8b053db2214d9c332a977d226c"}],"database_specific":{"cpe":"cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"0"},{"fixed":"1.33.2"}],"source":["CPE_RANGE","REFERENCES"]}}],"versions":["v1.33.0","v1.33.1","v1.33.0rc2","v1.33.0rc1","v1.32.0rc1","v1.31.0rc1","v1.30.0rc1","v1.29.0rc1","v1.27.0rc1","v1.24.0rc1","v1.23.0rc1","v1.17.0rc1","v1.18.0rc1","v1.16.0rc1","v1.15.0rc1","v1.14.0rc1","v1.12.0rc1","v1.6.0rc1","v1.11.0rc1","v1.3.0rc1","v1.1.0rc2","v1.1.0rc1","v1.10.0rc1","v1.9.0rc1","v1.9.0.dev2","v1.9.0.dev1","v1.8.0rc1","v1.5.0rc1","v1.4.0rc1","v0.99.5.1.dev0","v0.99.4rc1","v0.99.2rc1","v0.99.1rc1","hhs-8","hhs-7","hhs-6","hhs-5","hhs-3","hhs-2","hhs-1","v0.32.2","v0.32.0","v0.32.0rc1","v0.28.0-rc1","v0.25.0-rc1","v0.23.0-rc2","v0.23.0-rc1","v0.18.5","v0.18.4","v0.18.3","v0.18.2","v0.18.1","v0.18.0","v0.17.3","v0.17.2","v0.17.1","v0.17.0","v0.16.1-r1","v0.16.1","v0.16.0","v0.14.0","v0.13.3","v0.13.2","v0.13.1","v0.12.0","v0.11.1","v0.11.0-r2","v0.11.0-r1","v0.11.0","v0.10.0-r2","v0.10.0-r1","v0.10.0","v0.9.3","v0.9.2-r2","v0.9.2-r1","v0.9.2","v0.9.1","v0.9.0-r5","v0.9.0-r4","v0.9.0-r3","v0.9.0-r2","v0.9.0-r1","v0.9.0","v0.8.1-r4","v0.8.1-r3","v0.8.1-r2","v0.8.1-r1","v0.8.1","v0.8.0","v0.7.1-r4","v0.7.1-r3","v0.7.1-r2","v0.7.1-r1","v0.7.1","v0.7.0f","v0.7.0e","v0.7.0d","v0.7.0c","v0.7.0b","v0.7.0a","v0.7.0","v0.6.1f","v0.6.1e","v0.6.1d","v0.6.1c","v0.6.1b","v0.6.1a","v0.6.1","v0.6.0b","v0.6.0a","v0.6.0","v0.5.4a","v0.5.4","v0.5.3c","v0.5.3b","v0.5.3a","v0.5.3","v0.5.2","v0.5.1","v0.5.0","v0.4.2","v0.4.1","v0.3.4","v0.3.3","v0.3.0","v0.2.2","v0.2.1a","v0.2.1","v0.2.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-29471.json"}}],"references":[{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/"},{"type":"ADVISORY","url":"https://github.com/matrix-org/synapse/releases/tag/v1.33.2"},{"type":"FIX","url":"https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c"},{"type":"FIX","url":"https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85"}],"database_specific":{"unresolved_ranges":[{"cpes":["cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*"],"extracted_events":[{"introduced":"34"},{"last_affected":"34"}],"source":"CPE_STRING","vendor_product":"fedoraproject:fedora"}]},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}