CVE-2021-29471
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.
How to fix
- matrix synapse1.33.2 or later
- matrix-synapse1.33.2 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| matrix synapse | v < 1.33.2 | 1.33.2 |
| fedoraproject fedora | 34 | — |
| matrix-synapsePyPI | v < 1.33.2 | 1.33.2 |
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