CVE-2021-21392 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 1.28.0 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.

CVSS Vector

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

Reference

https://pypi.org/project/matrix-synapse/ https://github.com/matrix-org/synapse/security/advisories/GHSA-5wrh-4jwv-5w78 https://github.com/matrix-org/synapse/pull/9240 https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

REQUIRED

Confidentiality Impact

UNCHANGED

Integrity Impact

LOW

Availability Impact

HIGH

Base Score

NONE

Base Severity

6.3