CVE-2023-41318

matrix-media-repo: Unsafe media served inline on download endpoints

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

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.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2023-41318 has a CVSS score of 4.1 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.3.0); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

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.

1. What is CVE-2023-41318? CVE-2023-41318 is a medium-severity cross-site scripting (XSS) vulnerability in github.com/turt2live/matrix-media-repo (go), affecting versions < 1.3.0. It is fixed in 1.3.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2023-41318? CVE-2023-41318 has a CVSS score of 4.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/turt2live/matrix-media-repo are affected by CVE-2023-41318? github.com/turt2live/matrix-media-repo (go) versions < 1.3.0 is affected.
4. Is there a fix for CVE-2023-41318? Yes. CVE-2023-41318 is fixed in 1.3.0. Upgrade to this version or later.
5. Is CVE-2023-41318 exploitable, and should I be worried? Whether CVE-2023-41318 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-41318 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-41318? Upgrade github.com/turt2live/matrix-media-repo to 1.3.0 or later.