CVE-2021-21274 Detail

Current 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 1.25.0, a malicious homeserver could redirect requests to their .well-known file to a large file. This can lead to a denial of service attack where homeservers will consume significantly more resources when requesting the .well-known file of a malicious homeserver. This affects any server which accepts federation requests from untrusted servers. Issue is resolved in version 1.25.0. As a workaround the `federation_domain_whitelist` setting can be used to restrict the homeservers communicated with over federation.


View Analysis Description

Severity



CVSS 3.x Severity and Metrics:

NIST CVSS score
NIST: NVD
Base Score:  6.5 MEDIUM
Vector:  CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
Base Score:  4.3 MEDIUM
Vector:  CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L


NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: It is possible that the NVD CVSS may not match that of the CNA. The most common reason for this is that publicly available information does not provide sufficient detail or that information simply was not available at the time the CVSS vector string was assigned.

References to Advisories, Solutions, and Tools

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Hyperlink Resource
https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6 Patch  Third Party Advisory 
https://github.com/matrix-org/synapse/pull/8950 Patch  Third Party Advisory 
https://github.com/matrix-org/synapse/releases/tag/v1.25.0 Third Party Advisory 
https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8 Patch  Third Party Advisory 
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/

Weakness Enumeration

CWE-ID CWE Name Source
CWE-400 Uncontrolled Resource Consumption Contributor acceptance level GitHub, Inc.  

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Change History

2 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2021-21274
NVD Published Date:
02/26/2021
NVD Last Modified:
08/01/2021
Source:
GitHub, Inc.