CVE-2021-21392

Severity CVSS v4.0:

Pending analysis

Type:

CWE-601 URL Redirection to Untrusted Site ('Open Redirect')

Publication date:

12/04/2021

Last modified:

07/11/2023

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.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:N CVSS v3.1 Severity and Metrics:

Base Score: 6.30 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:N

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): Low
User Interaction (UI): Required
Scope (S): Unchanged
Confidentiality (C): Low
Integrity (I): High
Availability (A): None

Base Score 3.x

6.30

Severity 3.x

MEDIUM

Vector 2.0

AV:N/AC:M/Au:S/C:P/I:P/A:N CVSS v2.0 Severity and Metrics:

Base Score: 4.90 MEDIUM
Vector: AV:N/AC:M/Au:S/C:P/I:P/A:N

Attack Vector (AV): Network
Attack Complexity (AC): Medium
Authentication (Au): Single
Confidentiality (C): Physical
Integrity (I): Physical
Availability (A): None