Bug 1959541 (CVE-2021-29471) - CVE-2021-29471 matrix-synapse: Denial-of-service when processing moderate length events
Summary: CVE-2021-29471 matrix-synapse: Denial-of-service when processing moderate len...
Keywords:
Status: CLOSED UPSTREAM
Alias: CVE-2021-29471
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1959542
Blocks:
TreeView+ depends on / blocked
 
Reported: 2021-05-11 18:10 UTC by Pedro Sampaio
Modified: 2021-05-11 20:34 UTC (History)
2 users (show)

Fixed In Version:
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Last Closed: 2021-05-11 20:34:05 UTC


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Description Pedro Sampaio 2021-05-11 18:10:21 UTC
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.

References:

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

Comment 1 Pedro Sampaio 2021-05-11 18:10:50 UTC
Created matrix-synapse tracking bugs for this issue:

Affects: fedora-all [bug 1959542]

Comment 2 Product Security DevOps Team 2021-05-11 20:34:05 UTC
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.


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