# CVE-2021-29453: Denial of service through memory exhaustion

> A malicious user can cause denial of service by uploading crafted images that exhaust server memory during thumbnailing in matrix-media-repo.

- **Severity:** Medium 5.7 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 19 Apr 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-j889-h476-hh9h

## What is CVE-2021-29453?

CVE-2021-29453 is a medium-severity denial of service vulnerability in turt2live matrix-media-repo, published on 19 Apr 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

matrix-media-repo is an open-source multi-domain media repository for Matrix. Versions 1.2.6 and earlier of matrix-media-repo do not properly handle malicious images which are crafted to be small in file size, but large in complexity. A malicious user could upload a relatively small image in terms of file size, using particular image formats, which expands to have extremely large dimensions during the process of thumbnailing. The server can be exhausted of memory in the process of trying to load the whole image into memory for thumbnailing, leading to denial of service. Version 1.2.7 has a fix for the vulnerability.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2021-29453?

It affects 1 product.


Products: Matrix-Media-Repo Project Matrix-Media-Repo.

## How do I fix CVE-2021-29453?

No fix has been published for CVE-2021-29453 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-29453 being exploited?

There is no known exploitation of CVE-2021-29453 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-29453 and fix it if it is affected.

What it is: CVE-2021-29453 is a medium-severity denial of service vulnerability in turt2live matrix-media-repo, published on 19 Apr 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-29453 in the wild and no public exploit code.

Affected product: turt2live matrix-media-repo. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2021-29453/ (Markdown: https://insights.sbomify.com/CVE-2021-29453/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-29453
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-29453
- OSV: https://osv.dev/vulnerability/CVE-2021-29453

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-29453/
Summaries are generated and may contain mistakes; the official description above is the record.