Bug 1959541 (CVE-2021-29471)

Summary:	CVE-2021-29471 matrix-synapse: Denial-of-service when processing moderate length events
Product:	[Other] Security Response	Reporter:	Pedro Sampaio <psampaio>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED UPSTREAM	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	djc, fedora
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Fixed In Version:		Doc Type:	If docs needed, set a value
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Last Closed:	2021-05-11 20:34:05 UTC	Type:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
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Bug Depends On:	1959542
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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.