"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 by https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c.
A potential workaround might be to prevent users from making custom push rules, by blocking such requests at a reverse-proxy.
If you have any questions or comments about this advisory, email us at security@matrix.org.
{ "nvd_published_at": "2021-05-11T15:15:00Z", "cwe_ids": [ "CWE-331", "CWE-400" ], "severity": "MODERATE", "github_reviewed": true, "github_reviewed_at": "2021-05-11T17:19:15Z" }