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.
CVE-2021-21274
Published Date: 2021-02-26T18:15Z
Last Modified: 2023-11-07T03:29Z
CVSS Score: 6.5 (MEDIUM)
EPSS Score: 0.17%
Risk Score: 4.55 (MEDIUM)
Risk Score based on CVSS score and EPSS. This score is for reference purposes and is not internationally recognized.
CVSS:
6.5 |
EPSS:
0.17%
Mitre ATT&CK Technical v15.1
T1153 – Source
T1583.004 – Server
T1059.006 – Python
T1584.004 – Server
T1053.002 – At
Technical Analysis & Mitigation Measures
Reference Links
https://github.com/matrix-org/synapse/releases/tag/v1.25.0
https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6
https://github.com/matrix-org/synapse/pull/8950
https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/
Vendor - Produce - Version
synapse - matrix, fedora - fedoraproject
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