How severe is CVE-2024-36403?

CVE-2024-36403 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2024-36403?

CVE-2024-36403 affects the following packages: github.com/t2bot/matrix-media-repo (Go). Ecosystems affected: Go.

How do I fix CVE-2024-36403?

Update github.com/t2bot/matrix-media-repo to 1.3.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-36403 is resolved across your whole dependency graph.

How do I detect CVE-2024-36403 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/t2bot/matrix-media-repo. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2024-36403 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2024-36403?

O3 pinpoints whether CVE-2024-36403 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2024-36403 actively exploited in the wild?

No public exploit code has been indexed for CVE-2024-36403 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2024-36403?

CVE-2024-36403 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 47th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2024-36403 published, and has it been updated?

CVE-2024-36403 was published on January 16, 2025 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2024-36403: matrix-media-repo Denial of Service (Medium 5.3)

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk47th percentile+0.57%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🐹github.com/t2bot/matrix-media-repo

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/t2bot/matrix-media-repo`	all versions	1.3.5

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/t2bot/matrix-media-repo. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/t2bot/matrix-media-repo to 1.3.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-36403 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2024-36403 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2024-36403. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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

O3 Security · Impact-Aware SCA

Is CVE-2024-36403 in your dependencies?

O3 detects CVE-2024-36403 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

CVE-2024-36403