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

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

- **Severity:** Medium 6.6 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 31 Jul 2026
- **Updated:** 31 Jul 2026
- **Also known as:** GHSA-623p-8r6m-hwc6

## 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 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-14539?

It affects 1 product.


Products: 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.

## Is CVE-2026-14539 being exploited?

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

## Other vulnerabilities in Google mcp-toolbox

- [CVE-2026-11720](https://insights.sbomify.com/CVE-2026-11720/): Path Traversal in googleapis/mcp-toolbox HTTP Tool URL Builder (critical 9.3)
- [CVE-2026-11717](https://insights.sbomify.com/CVE-2026-11717/): googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken) (critical 9.3)
- [CVE-2026-11718](https://insights.sbomify.com/CVE-2026-11718/): googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken) (critical 9.3)
- [CVE-2026-15829](https://insights.sbomify.com/CVE-2026-15829/): SQL Injection and Security Boundary Bypass in googleapis/mcp-toolbox (high 8.6)
- [CVE-2026-11719](https://insights.sbomify.com/CVE-2026-11719/): MCP Toolbox for Databases: authenticated authorization bypass (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-14539 and fix it if it is affected.

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

Affected product: Google mcp-toolbox. 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-2026-14539/ (Markdown: https://insights.sbomify.com/CVE-2026-14539/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-14539
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-14539
- OSV: https://osv.dev/vulnerability/CVE-2026-14539

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-14539/
Summaries are generated and may contain mistakes; the official description above is the record.