# CVE-2026-55241: Checkmate: Pre-auth Denial of Service via File Upload on Registration

> Unauthenticated attackers can crash the Checkmate server by uploading oversized files during registration, exhausting memory resources.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 21 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** GHSA-9xvg-x28f-m78m

## What is CVE-2026-55241?

CVE-2026-55241 is a high-severity denial of service vulnerability in bluewave-labs Checkmate, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Checkmate is an open-source, self-hosted tool designed to track and monitor server hardware, uptime, response times, and incidents in real-time with beautiful visualizations. Prior to 3.9.1, the public POST /api/v1/auth/register route in server/src/api/routes/authRoutes.ts passes multipart profileImage uploads through in-memory Multer parsing before registration validation, without file-size, file-count, or MIME-type limits in server/src/api/middleware/upload.ts. An unauthenticated attacker can submit concurrent oversized files that are buffered before invalid registration or invite-token checks reject the request, exhausting memory and crashing or destabilizing the backend. This issue is fixed in version 3.9.1.

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

## Which versions are affected by CVE-2026-55241?


## How do I fix CVE-2026-55241?

No fix has been published for CVE-2026-55241 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-55241 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55241 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55241 and fix it if it is affected.

What it is: CVE-2026-55241 is a high-severity denial of service vulnerability in bluewave-labs Checkmate, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55241 exists.

Affected product: bluewave-labs Checkmate. 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-2026-55241/ (Markdown: https://insights.sbomify.com/CVE-2026-55241/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55241
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55241
- OSV: https://osv.dev/vulnerability/CVE-2026-55241

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-55241/
Summaries are generated and may contain mistakes; the official description above is the record.