{"id":"DEBIAN-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such requests at a reverse-proxy.","modified":"2026-08-11T20:49:52.858309174Z","published":"2021-05-11T15:15:08.507Z","withdrawn":"2026-08-11T20:49:52.858309049Z","upstream":["CVE-2021-29471"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2021-29471"}],"affected":[{"package":{"name":"matrix-synapse","ecosystem":"Debian:14","purl":"pkg:deb/debian/matrix-synapse?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.33.2-1"}]}],"versions":["0.19.2+dfsg-3","0.19.2+dfsg-4","0.19.2+dfsg-5","0.19.2+dfsg-6","0.24.0+dfsg-1","0.27.2+dfsg-1","0.28.0+dfsg-1","0.28.0+dfsg-2","0.28.1+dfsg-1","0.29.1+dfsg-1","0.30.0+dfsg-1","0.31.0+dfsg-1","0.31.0+dfsg-2","0.31.1+dfsg-1","0.31.1+dfsg-2","0.31.2+dfsg-1","0.32.2+dfsg-1","0.33.0+dfsg-1","0.33.1+dfsg-1","0.33.2+dfsg-1","0.33.2+dfsg-2","0.33.2+dfsg-3","0.33.3-1","0.33.3-2","0.33.3.1-1","0.33.4-1","0.33.4-1~bpo9+1","0.33.8-1","0.33.9-2","0.33.9-2~bpo9+1","0.34.0-1","0.34.0-2","0.34.0-3","0.34.0-3~bpo9+1","0.34.0-3~bpo9+2","0.34.0~rc2-1","0.34.1.1-1","0.34.1.1-2","0.34.1.1-2~bpo9+1","0.34.1.1-3","0.34.1.1-3~bpo9+1","0.34.1.1-3~bpo9+2","0.34.1.1-4","0.99.0-1","0.99.0-1~bpo9+1","0.99.0-1~bpo9+2","0.99.0-1~bpo9+3","0.99.1.1-1","0.99.2-1","0.99.2-1~bpo9+1","0.99.2-1~bpo9+2","0.99.2-2","0.99.2-3","0.99.2-4","0.99.2-5","0.99.2-5~bpo9+1","0.99.2-6","0.99.3.2-1","0.99.5.1-1","0.99.5.2-1","1.0.0-1","1.0.0-2","1.0.0-2~bpo10+1","1.1.0-1","1.10.0-1","1.10.0-2","1.11.0-1","1.11.1-1","1.11.1-1~bpo10+1","1.12.0-1","1.12.0-1~bpo10+1","1.12.3-1","1.12.3-1~bpo10+1","1.12.4-1","1.12.4-1~bpo10+1","1.13.0-1","1.13.0-1~bpo10+1","1.15.0-1","1.15.1-1","1.15.1-1~bpo10+1","1.15.1-1~bpo10+2","1.15.2-1","1.16.0-1","1.17.0-1","1.17.0-1~bpo10+1","1.18.0-1","1.18.0-1~bpo10+1","1.19.0-1","1.19.0-1~bpo10+1","1.19.1-1","1.19.1-1~bpo10+1","1.19.1-1~bpo10+2","1.19.1-1~bpo10+3","1.19.2-1","1.19.3-1","1.2.1-1","1.2.1-1~bpo10+1","1.2.1-1~bpo10+2","1.2.1-2","1.20.0-1","1.20.1-1","1.20.1-1~bpo10+1","1.21.1-1","1.21.2-1","1.21.2-1~bpo10+1","1.22.1-1","1.22.1-1~bpo10+1","1.22.1-2","1.22.1-2~bpo10+1","1.23.0-1","1.23.0-1~bpo10+1","1.24.0-1","1.24.0-1~bpo10+1","1.24.0-2","1.25.0-1","1.25.0-1~bpo10+1","1.25.0-2","1.26.0-1","1.26.0-1~bpo10+1","1.26.0-1~bpo10+2","1.26.0-1~bpo10+3","1.26.0-2","1.26.0-3","1.27.0-1","1.27.0-1~bpo10+1","1.27.0-1~bpo10+2","1.27.0-1~bpo10+3","1.28.0-1","1.28.0-1~bpo10+1","1.28.0-1~bpo10+2","1.29.0-1","1.3.0-1","1.3.0-1~bpo10+1","1.30.0-1","1.31.0-1","1.31.0-2","1.4.0-1","1.4.0~rc1-1","1.5.0-1","1.5.0~rc1-1","1.5.1-1","1.5.1-1~bpo10+1","1.6.0-1","1.6.1-1","1.6.1-1~bpo10+1","1.7.0-1","1.7.0-2","1.7.1-1","1.7.2-1","1.7.2-1~bpo10+1","1.7.3-1","1.7.3-1~bpo10+1","1.8.0-1","1.9.0-1","1.9.0-1~bpo10+1","1.9.1-1","1.9.1-1~bpo10+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-29471.json"}}],"schema_version":"1.8.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}