Bug 1949111 (CVE-2021-21392)

Summary:	CVE-2021-21392 matrix-synapse: IP blacklist bypass via transitional IPv6 addresses on dual-stack networks
Product:	[Other] Security Response	Reporter:	Michael Kaplan <mkaplan>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED UPSTREAM	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	djc, fedora
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	matrix-synapse 1.28.0	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-04-13 22:46:43 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1949112
Bug Blocks:

Description Michael Kaplan 2021-04-13 12:57:29 UTC

In Synapse before version 1.28.0 requests to user provided domains were not restricted to external IP addresses when transitional IPv6 addresses were used. Outbound requests to federation, identity servers, when calculating the key validity for third-party invite events, sending push notifications, and generating URL previews are affected. This could cause Synapse to make requests to internal infrastructure on dual-stack networks. See referenced GitHub security advisory for details and workarounds.

Comment 1 Michael Kaplan 2021-04-13 12:57:34 UTC

External References:

https://github.com/matrix-org/synapse/pull/9240
https://github.com/matrix-org/synapse/security/advisories/GHSA-5wrh-4jwv-5w78

Comment 2 Michael Kaplan 2021-04-13 12:57:51 UTC

Created matrix-synapse tracking bugs for this issue:

Affects: fedora-all [bug 1949112]

Comment 3 Product Security DevOps Team 2021-04-13 22:46:43 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.