CVE-2026-11624: MCP Toolbox for Databases has an Origin Validation Error

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.2%, percentile 12: FIRST’s model estimates a 0.2% chance of exploitation activity in the next 30 days, higher than 12% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Only applies if your dependency tree includes github.com/googleapis/mcp-toolbox (Go) < 0.25.0, fixed in 0.25.0. Check your lockfile, including transitive dependencies.

What it is

The Model Context Protocol has a security warning advising servers to validate the "Origin" header on all incoming connections to prevent DNS rebinding attacks. Prior to the v0.25.0 release, users had no way to validate the origin's host. In v0.25.0, a new "--allowed-hosts" flag was introduced alongside the existing "--allowed-origins" flag, enabling users to specify permitted hosts at server startup. Both flags default to "", allowing users to implement strict access controls as needed without breaking existing setups. If either flag is set to "", the server will output a startup warning about potential vulnerabilities. Documentation has also been updated to highlight these security considerations.

From the GitHub advisory

The Model Context Protocol has a security warning advising servers to validate the "Origin" header on all incoming connections to prevent DNS rebinding attacks. Prior to the v0.25.0 release, users had no way to validate the origin's host. In v0.25.0, a new "--allowed-hosts" flag was introduced alongside the existing "--allowed-origins" flag, enabling users to specify permitted hosts at server startup. Both flags default to "", allowing users to implement strict access controls as needed without breaking existing setups. If either flag is set to "", the server will output a startup warning about potential vulnerabilities. Documentation has also been updated to highlight these security considerations.

Weakness type: CWE-346.

Product: github.com/googleapis/mcp-toolbox (Go) · Assigned by: Google · Published: 2026-06-13

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: active

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.22% probability of exploitation activity in the next 30 days; percentile 12.

Timeline

• 2026-06-13 — CVE record published by Google
• 2026-06-13 — GitHub-reviewed advisory GHSA-76g7-m3xw-x9gr published (critical)
• 2026-06-15 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-76g7-m3xw-x9gr github.com
2. CVE.org record CVE-2026-11624 cve.org
3. NVD entry CVE-2026-11624 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

Critical Go advisories · Today’s Security Digest