MCP Toolbox for Databases (googleapis/mcp-toolb…: Improper Authentication
CVE-2026-11718 is a critical-severity improper authentication vulnerability in MCP Toolbox for Databases (googleapis/mcp-toolbox) from Google, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected MCP Toolbox for Databases (googleapis/mcp-toolbox) versions: 1.0.0 through 1.3.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.18% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of MCP Toolbox for Databases (googleapis/mcp-toolbox) you run against the affected versions below, and install the vendor's latest release.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| MCP Toolbox for Databases (googleapis/mcp-toolbox) | 1.0.0 through 1.3.0 | Not stated | |
| Mcp Toolbox For Databases | 1.0.0 through 1.3.0 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.3 | Critical | CNA (google.com) |
| CVSS 3.1 | 9.1 | Critical | NVD |
Official description
An authentication bypass vulnerability exists in the generic opaque token validation path (validateOpaqueToken) of googleapis/mcp-toolbox. When the toolbox validates an opaque token via an OAuth 2.0 introspection endpoint (RFC 7662), it decodes the response into an introspectResp struct. However, the subsequent claim-checking logic (validateClaims) evaluates the issuer condition as if a.issuer != "" && iss != "". If the external OAuth provider's introspection response omits the optional iss (issuer) field completely, the variable iss defaults to an empty string. This causes the conditional block to evaluate to false and be skipped silently. Consequently, the application accepts tokens issued by unauthorized or unintended third-party identity providers.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Authentication
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
How developers prevent this class of flaw
- Use an authentication framework or library such as the OWASP ESAPI Authentication feature.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other vulnerabilities in MCP Toolbox for Databases (googleapis/mcp-toolbox)
- 7.5 High severity
- 8.1 High severity
- 9.1 Critical severity
- 8.1 High severity
- 9.1 Critical severity
Recent Improper Authentication vulnerabilities
- 9.1 Critical severity
- 8.1 High severity
- 8.1 High severity
- 7.5 High severity
- 9.8 Critical severity
- 8.2 High severity
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