CVE-2021-29471
First published: Tue May 11 2021(Updated: )
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.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Matrix Synapse | <1.33.2 | |
| Fedoraproject Fedora | =34 |
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Reference Links
- https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c
- https://github.com/matrix-org/synapse/releases/tag/v1.33.2
- https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/
Frequently Asked Questions
What is CVE-2021-29471?
CVE-2021-29471 is a vulnerability in the Synapse Matrix reference homeserver that allows "Push rules" to match events under certain conditions.
What is the severity of CVE-2021-29471?
CVE-2021-29471 has a severity rating of 5.3 (medium).
Which software is affected by CVE-2021-29471?
The Matrix Synapse version up to 1.33.2 and Fedoraproject Fedora version 34 are affected by CVE-2021-29471.
How can I fix CVE-2021-29471?
To fix CVE-2021-29471, upgrade to Synapse version 1.33.2 or later.
Where can I find more information about CVE-2021-29471?
You can find more information about CVE-2021-29471 in the references provided: [Link 1](https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c), [Link 2](https://github.com/matrix-org/synapse/releases/tag/v1.33.2), [Link 3](https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85).
- collector/nvd-index
- vendor/matrix
- canonical/matrix synapse
- vendor/fedoraproject
- canonical/fedoraproject fedora
- version/fedoraproject fedora/34