Headline
GHSA-5crw-6j7v-xc72: matrix-media-repo: Unsafe media served inline on download endpoints
Impact
A malicious user can upload an SVG image containing JavaScript to their server. When matrix-media-repo is asked to serve that media via the /_matrix/media/(r0|v3)/download endpoint, it would be served with a Content-Disposition of inline. This can allow JavaScript to run in the browser if a client links to the /download endpoint directly.
Server operators which do not share a domain between matrix-media-repo and other services are not affected, but are encouraged to upgrade regardless.
Patches
https://github.com/turt2live/matrix-media-repo/commit/77ec2354e8f46d5ef149d1dcaf25f51c04149137 and https://github.com/turt2live/matrix-media-repo/commit/bf8abdd7a5371118e280c65a8e0ec2b2e9bdaf59 fix the issue. Operators should upgrade to v1.3.0 as soon as possible.
Workarounds
The Content-Disposition header can be overridden by the reverse proxy in front of matrix-media-repo to always use attachment, defeating this issue at the cost of “worse” user experience when clicking download links.
References
https://developer.mozilla.org/en-US/docs/Web/SVG/Element/script
Impact
A malicious user can upload an SVG image containing JavaScript to their server. When matrix-media-repo is asked to serve that media via the /_matrix/media/(r0|v3)/download endpoint, it would be served with a Content-Disposition of inline. This can allow JavaScript to run in the browser if a client links to the /download endpoint directly.
Server operators which do not share a domain between matrix-media-repo and other services are not affected, but are encouraged to upgrade regardless.
Patches
turt2live/matrix-media-repo@77ec235 and turt2live/matrix-media-repo@bf8abdd fix the issue. Operators should upgrade to v1.3.0 as soon as possible.
Workarounds
The Content-Disposition header can be overridden by the reverse proxy in front of matrix-media-repo to always use attachment, defeating this issue at the cost of “worse” user experience when clicking download links.
References
https://developer.mozilla.org/en-US/docs/Web/SVG/Element/script
References
- GHSA-5crw-6j7v-xc72
- turt2live/matrix-media-repo@77ec235
- turt2live/matrix-media-repo@bf8abdd
- https://developer.mozilla.org/en-US/docs/Web/SVG/Element/script
Related news
matrix-media-repo is a highly customizable multi-domain media repository for the Matrix chat ecosystem. In affected versions an attacker could upload a malicious piece of media to the media repo, which would then be served with `Content-Disposition: inline` upon download. This vulnerability could be leveraged to execute scripts embedded in SVG content. Commits `77ec235` and `bf8abdd` fix the issue and are included in the 1.3.0 release. Operators should upgrade to v1.3.0 as soon as possible. Operators unable to upgrade should override the `Content-Disposition` header returned by matrix-media-repo as a workaround.