GHSA-x345-32rc-8h85

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GHSA-x345-32rc-8h85

Summary: Denial of service attack via push rule patterns in matrix-synapse

Details: ### Impact "Push rules" can specify [conditions](https://matrix.org/docs/spec/client_server/r0.6.1#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. ### Patches The issue is patched by https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c. ### Workarounds A potential workaround might be to prevent users from making custom push rules, by blocking such requests at a reverse-proxy. ### For more information If you have any questions or comments about this advisory, email us at [email protected].

References: https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85, https://nvd.nist.gov/vuln/detail/CVE-2021-29471, https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c, https://github.com/matrix-org/synapse, https://github.com/matrix-org/synapse/releases/tag/v1.33.2, https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-135.yaml, https://lists.fedoraproject.org/archives/list/[email protected]/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY