CVE-2021-21274
First published: Fri Feb 26 2021(Updated: )
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.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Matrix Synapse | >=0.99.0<1.25.0 | |
| Fedoraproject Fedora | =34 |
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Reference Links
- https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6
- https://github.com/matrix-org/synapse/pull/8950
- https://github.com/matrix-org/synapse/releases/tag/v1.25.0
- https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/
Frequently Asked Questions
What is CVE-2021-21274?
CVE-2021-21274 is a vulnerability in Synapse, a Matrix reference homeserver, that allows a malicious server to redirect requests to a large file.
What is Synapse?
Synapse is a Matrix reference homeserver written in Python that provides an ecosystem for open federated Instant Messaging and VoIP.
What is the severity of CVE-2021-21274?
CVE-2021-21274 has a severity of 6.5 (Medium).
How can CVE-2021-21274 be fixed?
CVE-2021-21274 can be fixed by upgrading to Synapse version 1.25.0 or later.
Are there any references for CVE-2021-21274?
Yes, you can find references for CVE-2021-21274 at the following links: [GitHub Commit](https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6), [GitHub Pull Request](https://github.com/matrix-org/synapse/pull/8950), [GitHub Release](https://github.com/matrix-org/synapse/releases/tag/v1.25.0).
- collector/nvd-index
- agent/references
- agent/severity
- agent/author
- agent/type
- agent/event
- vendor/matrix
- canonical/matrix synapse
- version/matrix synapse/0.99.0
- vendor/fedoraproject
- canonical/fedoraproject fedora
- version/fedoraproject fedora/34