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.
The product does not properly control the allocation and maintenance of a limited resource.
The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.
| Link | Tags |
|---|---|
| https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8 | third party advisory patch |
| https://github.com/matrix-org/synapse/releases/tag/v1.25.0 | third party advisory |
| https://github.com/matrix-org/synapse/pull/8950 | third party advisory patch |
| https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6 | third party advisory patch |
| https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/ | vendor advisory |