# CVE-2026-14539: Google mcp-toolbox denial of service in HTTP handler

Source: https://junglewise.ai/threats/cve-2026-14539-google-mcp-toolbox-denial-of-service-in-http-handler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-31. Updated: 2026-07-31  
License: CC BY 4.0 with a link back

CVE-2026-14539 · Severity: info · CVSS 6.6 · Published 2026-07-31

Google mcp-toolbox, a set of tools for the Model Context Protocol, is vulnerable to a denial-of-service attack. An unauthenticated attacker can send a single, specially crafted large request that consumes all available system memory. This can cause the application to crash, leading to service outages and impacting operational availability.

Technologies: [Google MCP Toolbox](https://junglewise.ai/threats/technologies/mcp-toolbox). Vendors: [Google](https://junglewise.ai/threats/vendors/google).

## Quick answers

**Is CVE-2026-14539 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-14539 being exploited in the wild.

**How severe is CVE-2026-14539?** Informational severity, with a CVSS score of 6.6, published 31 July 2026.

**Which products and versions are affected?** Google MCP Toolbox up to and including 1.4.0.

**Is there a fix for CVE-2026-14539?** A patch was published on 2026-05-12: Fix submitted via Pull Request #3216 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-14539 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-14539?** Check whether you run Google MCP Toolbox at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in the /mcp endpoint handler of Google mcp-toolbox due to the use of an unrestricted buffer loop (io.ReadAll) when reading incoming HTTP payloads. The component fails to implement defensive constraints such as http.MaxBytesReader or Content-Length enforcement. A remote, unauthenticated attacker can exploit this by submitting a massive HTTP request body, leading to linear memory consumption and an eventual Out-Of-Memory (OOM) termination of the process. The issue is addressed in pull request #3216 by implementing a 10 MiB limit using http.MaxBytesReader.

## Affected products

- Google mcp-toolbox up to and including 1.4.0

## Timeline

- 2026-05-12: patched: Fix submitted via Pull Request #3216
- 2026-07-31: advisory: NVD publication date

## References

- [https://github.com/googleapis/mcp-toolbox/pull/3216](https://github.com/googleapis/mcp-toolbox/pull/3216)

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