# CVE-2024-36403: Denial of service/high operating costs through unauthenticated downloads in Matrix Media Repo

> Unauthenticated attackers can exhaust disk space or incur high cloud costs by triggering unbounded media downloads in Matrix Media Repo.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Jan 2025
- **Updated:** 12 Feb 2025
- **Also known as:** GHSA-vc2m-hw89-qjxf, GO-2025-3401

## What is CVE-2024-36403?

CVE-2024-36403 is a medium-severity denial of service vulnerability in t2bot matrix-media-repo, published on 16 Jan 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Matrix Media Repo (MMR) is a highly configurable multi-homeserver media repository for Matrix. MMR before version 1.3.5 is vulnerable to unbounded disk consumption, where an unauthenticated adversary can induce it to download and cache large amounts of remote media files. MMR's typical operating environment uses S3-like storage as a backend, with file-backed store as an alternative option. Instances using a file-backed store or those which self-host an S3 storage system are therefore vulnerable to a disk fill attack. Once the disk is full, authenticated users will be unable to upload new media, resulting in denial of service. For instances configured to use a cloud-based S3 storage option, this could result in high service fees instead of a denial of service. MMR 1.3.5 introduces a new default-on "leaky bucket" rate limit to reduce the amount of data a user can request at a time. This does not fully address the issue, but does limit an unauthenticated user's ability to request large amounts of data. Operators should note that the leaky bucket implementation introduced in MMR 1.3.5 requires the IP address associated with the request to be forwarded, to avoid mistakenly applying the rate limit to the reverse proxy instead. To avoid this issue, the reverse proxy should populate the X-Forwarded-For header when sending the request to MMR. Operators who cannot update may wish to lower the maximum file size they allow and implement harsh rate limits, though this can still lead to a large amount of data to be downloaded.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2024-36403?

3 open source packages ship an affected version, including github.com/t2bot/matrix-media-repo. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/t2bot/matrix-media-repo` | Go | All versions | 1.3.5 |
| `github.com/t2bot/matrix-media-repo` | Go | All versions | 1.3.5 |
| `github.com/t2bot/matrix-media-repo` | Go | All versions | 1.3.5 |

Products: T2bot Matrix-Media-Repo.

## How do I fix CVE-2024-36403?

Upgrade github.com/t2bot/matrix-media-repo to 1.3.5 or later.

## Is CVE-2024-36403 being exploited?

There is no known exploitation of CVE-2024-36403 in the wild and no public exploit code.

## Other vulnerabilities in t2bot matrix-media-repo

- [CVE-2024-56515](https://insights.sbomify.com/CVE-2024-56515/): Untrusted file formats can be thumbnailed, invoking potentially further untrusted decoders in Matrix Media Repo (medium 6.8)
- [CVE-2024-36402](https://insights.sbomify.com/CVE-2024-36402/): Unauthenticated writes to the media repository allow planting of problematic content in Matrix Media Repo (medium 5.3)
- [CVE-2024-52791](https://insights.sbomify.com/CVE-2024-52791/): Denial of service through memory exhaustion in Matrix Media Repo (medium 5.3)
- [CVE-2024-52602](https://insights.sbomify.com/CVE-2024-52602/): Server-Side Request Forgery (SSRF) on redirects and federation in Matrix Media Repo (medium 5.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-36403 and fix it if it is affected.

What it is: CVE-2024-36403 is a medium-severity denial of service vulnerability in t2bot matrix-media-repo, published on 16 Jan 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-36403 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/t2bot/matrix-media-repo (Go): affected all versions; fixed in 1.3.5
- github.com/t2bot/matrix-media-repo (Go): affected all versions; fixed in 1.3.5
- github.com/t2bot/matrix-media-repo (Go): affected all versions; fixed in 1.3.5

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2024-36403/ (Markdown: https://insights.sbomify.com/CVE-2024-36403/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-36403
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-36403
- OSV: https://osv.dev/vulnerability/CVE-2024-36403

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-36403/
Summaries are generated and may contain mistakes; the official description above is the record.