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

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-01-16 · updated 2026-06-17
Weakness: CWE-287

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.

Affected products

t2bot matrix-media-repo: before 1.3.5 — fixed in 1.3.5

How to fix

Upgrade to a fixed version: t2bot matrix-media-repo 1.3.5. Check the vendor advisory for mitigations.

References

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