Python
CVE-2021-21392
MEDIUM
Severity by source
AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:N
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
Lifecycle Timeline
1DescriptionNVD
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.
AnalysisAI
Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Rated medium severity (CVSS 6.3), this vulnerability is remotely exploitable, low attack complexity. This Open Redirect vulnerability could allow attackers to redirect users to malicious websites via URL manipulation.
Technical ContextAI
This vulnerability is classified as Open Redirect (CWE-601), which allows attackers to redirect users to malicious websites via URL manipulation. 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. Affected products include: Matrix Synapse, Fedoraproject Fedora. Version information: version 1.28.0.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Validate redirect destinations against an allowlist, avoid using user input in redirect URLs.
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