CVE-2021-21274
Denial of service attack via .well-known lookups
- State
- Published
- Severity
- 4.3 Medium
- Published
- Feb 26, 2021
- Updated
- Aug 3, 2024
- Reserved
- Dec 22, 2020
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 4.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L | GitHub_M |
Weaknesses
- CWE-400 Uncontrolled Resource Consumption
Affected Products
| Product | Versions |
|---|---|
synapsematrix-org |
|
References
- https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8
- https://github.com/matrix-org/synapse/releases/tag/v1.25.0
- https://github.com/matrix-org/synapse/pull/8950
- https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6
- FEDORA-2021-a627cfd31evendor-advisory
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