CVE-2021-21274
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2021-21274
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| debian | forky | fixed | 1.25.0-1 |
| debian | sid | fixed | 1.25.0-1 |
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| PyPI | matrix-synapse | >=0.99.0,<1.25.0 | 1.25.0 |
| PyPI | matrix-synapse | <ff5c4da1289cb5e097902b3e55b771be342c29d6||>=0.99.0,<1.25.0 | ff5c4da1289cb5e097902b3e55b771be342c29d6 |
References
- https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8
- https://nvd.nist.gov/vuln/detail/CVE-2021-21274
- https://github.com/matrix-org/synapse/pull/8950
- https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6
- https://github.com/matrix-org/synapse
- https://github.com/matrix-org/synapse/releases/tag/v1.25.0
- https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-132.yaml
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY
- https://security-tracker.debian.org/tracker/CVE-2021-21274
Verify integrity in audit chain (admin only). AS-IS.