Vulnerability Details : CVE-2021-21392

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.
Published 2021-04-12 22:15:13
Updated 2021-11-23 22:36:22
Source GitHub, Inc.
View at NVD,   CVE.org
Vulnerability category: Open redirect

Products affected by CVE-2021-21392

Exploit prediction scoring system (EPSS) score for CVE-2021-21392

EPSS FAQ
0.09%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 35 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2021-21392

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
4.9
 MEDIUM AV:N/AC:M/Au:S/C:P/I:P/A:N
6.8
4.9
 NIST
6.3
 MEDIUM CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:N
2.1
4.2
 NIST
6.3
 MEDIUM CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:N
2.1
4.2
 GitHub, Inc.

CWE ids for CVE-2021-21392

  • A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks.
    Assigned by:
    • nvd@nist.gov (Primary)
    • security-advisories@github.com (Secondary)

References for CVE-2021-21392

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