Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Matrix | Synapse | >= 0.99.0, < 1.25.0 |
| Fedoraproject | Fedora | 34 |
Related Weaknesses (CWE)
References
- https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342PatchThird Party Advisory
- https://github.com/matrix-org/synapse/pull/8950PatchThird Party Advisory
- https://github.com/matrix-org/synapse/releases/tag/v1.25.0Third Party Advisory
- https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8PatchThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342PatchThird Party Advisory
- https://github.com/matrix-org/synapse/pull/8950PatchThird Party Advisory
- https://github.com/matrix-org/synapse/releases/tag/v1.25.0Third Party Advisory
- https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8PatchThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
FAQ
What is CVE-2021-21274?
CVE-2021-21274 is a vulnerability with a CVSS score of 4.3 (MEDIUM). 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 mali...
How severe is CVE-2021-21274?
CVE-2021-21274 has been rated MEDIUM with a CVSS base score of 4.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-21274?
Check the references section above for vendor advisories and patch information. Affected products include: Matrix Synapse, Fedoraproject Fedora.