CVE-2026-14539 Denial of Service via Unrestricted Payload Buffering in MCP Toolbox

Medium 6.6 Published 31 Jul 2026 Updated 31 Jul 2026

Unauthenticated attackers can crash the MCP Toolbox server by sending oversized HTTP requests that exhaust system memory.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-14539?

CVE-2026-14539 is a medium-severity denial of service vulnerability in Google mcp-toolbox, published on 31 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

An allocation of resources without limits vulnerability in the HTTP handler component of Google mcp-toolbox versions up to and including 1.4.0 allows an unauthenticated attacker to cause a denial of service (DoS). The /mcp endpoint handler reads incoming payloads directly into system memory using an unrestricted buffer loop (io.ReadAll) without applying defensive constraints such as http.MaxBytesReader or pre-read Content-Length enforcement. By submitting a single, massive HTTP request body, an attacker can linearly consume available host memory until the runtime process is terminated by an Out-Of-Memory (OOM) error.

Weakness: CWE-770

Which versions are affected by CVE-2026-14539?

It affects 1 product.

Products include Google Mcp Toolbox for Databases.

How do I fix CVE-2026-14539?

No fix has been published for CVE-2026-14539 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-14539 being exploited?

There is no known exploitation of CVE-2026-14539 in the wild and no public exploit code.

Sources

Also known as GHSA-623p-8r6m-hwc6.