“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 [email protected].
github.com/matrix-org/synapse
github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c
github.com/matrix-org/synapse/releases/tag/v1.33.2
github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85
lists.fedoraproject.org/archives/list/[email protected]/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY
nvd.nist.gov/vuln/detail/CVE-2021-29471