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CVE-2021-29471

Published: 11 May 2021

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.

Priority

Medium

CVSS 3 base score: 5.3

Status

Package Release Status
matrix-synapse
Launchpad, Ubuntu, Debian
Upstream
Released (1.33.2-1)
Ubuntu 21.10 (Impish Indri) Needed

Ubuntu 21.04 (Hirsute Hippo) Needed

Ubuntu 20.04 LTS (Focal Fossa) Needed

Ubuntu 18.04 LTS (Bionic Beaver) Needed

Ubuntu 16.04 ESM (Xenial Xerus) Ignored
(out of standard support)
Ubuntu 14.04 ESM (Trusty Tahr) Does not exist

Patches:
Upstream: https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c