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.
History

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2021-02-26T17:25:16

Updated: 2024-08-03T18:09:15.070Z

Reserved: 2020-12-22T00:00:00

Link: CVE-2021-21274

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Modified

Published: 2021-02-26T18:15:12.237

Modified: 2023-11-07T03:29:42.630

Link: CVE-2021-21274

cve-icon Redhat

No data.