CVE-2024-36402: Unauthenticated writes to the media repository allow planting of problematic content in Matrix Media Repo

Vulnerability summary

CVE-2024-36402 is a medium (CVSS 5.3) Improper Authentication vulnerability in t2bot matrix-media-repo. EPSS estimates a 0.56% chance of exploitation in the next 30 days, higher than 46.9% of scored vulnerabilities.

Timeline

1. 16-01-2025
   PublishedVulnerability first disclosed.
2. 12-02-2025
   Last modifiedVulnerability information updated.

Description

Matrix Media Repo (MMR) is a highly configurable multi-homeserver media repository for Matrix. MMR before version 1.3.5 allows, by design, unauthenticated remote participants to trigger a download and caching of remote media from a remote homeserver to the local media repository. Such content then also becomes available for download from the local homeserver in an unauthenticated way. The implication is that unauthenticated remote adversaries can use this functionality to plant problematic content into the media repository. MMR 1.3.5 introduces a partial mitigation in the form of new endpoints which require authentication for media downloads. The unauthenticated endpoints will be frozen in a future release, closing the attack vector. Though extremely limited, server operators can use more strict rate limits based on IP address as a partial workaround.

• CWE-287Improper AuthenticationWhen an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.