CVE-2021-29471 Information

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.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Reference

https://github.com/matrix-org/synapse/releases/tag/v1.33.2 https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85 https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

LOW

Base Severity

5.3