CVE-2026-14539
Denial of Service via Unrestricted Payload Buffering in MCP Toolbox
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.
INFO
Published Date :
July 31, 2026, 2:16 a.m.
Last Modified :
Aug. 8, 2026, 12:20 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 14ed7db2-1595-443d-9d34-6215bf890778 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update mcp-toolbox to a patched version.
- Implement resource limits for HTTP request bodies.
- Validate Content-Length before reading request data.
- Use http.MaxBytesReader to limit payload size.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-14539.
| URL | Resource |
|---|---|
| https://github.com/googleapis/mcp-toolbox/pull/3216 | Issue Tracking Patch |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-14539 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-14539
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-14539 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-14539 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Aug. 08, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:google:mcp_toolbox_for_databases:*:*:*:*:*:*:*:* versions up to (excluding) 1.5.0 Added Reference Type Google Inc.: https://github.com/googleapis/mcp-toolbox/pull/3216 Types: Issue Tracking, Patch -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 31, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-14539', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-31T16:10:46.118537Z'} -
New CVE Received by [email protected]
Jul. 31, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Google', 'product': 'mcp-toolbox', 'versions': [{'status': 'affected', 'version': '0.0.0', 'versionType': 'semver', 'lessThanOrEqual': '1.4.0'}], 'defaultStatus': 'unaffected'}] Added 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-770 Added Reference https://github.com/googleapis/mcp-toolbox/pull/3216