Skip to content

Agentgateway is missing parameter sanitization in MCP to OpenAPI conversion

Moderate severity GitHub Reviewed Published Mar 4, 2026 in agentgateway/agentgateway • Updated Mar 6, 2026

Package

gomod github.com/agentgateway/agentgateway (Go)

Affected versions

< 0.12.0

Patched versions

0.12.0

Description

Summary

When converting MCP tools/call request to OpenAPI request, input path, query, and header values are not sanitized.

Details

When using the MCP to OpenAPI feature, the proxy lacks proper sanitization of input parameters in the MCP call, allowing:

  • Injection of additional path or query parameters.
  • Injection of additional headers.

Impacted Versions

This vulnerability is fixed in Agentgateway v0.12.0+. Users on older versions are recommended to upgrade to v0.12.0+.

This feature only impacts usage of the MCP to OpenAPI feature

Credits

Agentgateway extends its thanks to @spacewander for the report!

References

@howardjohn howardjohn published to agentgateway/agentgateway Mar 4, 2026
Published to the GitHub Advisory Database Mar 5, 2026
Reviewed Mar 5, 2026
Published by the National Vulnerability Database Mar 6, 2026
Last updated Mar 6, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(14th percentile)

Weaknesses

Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Learn more on MITRE.

CVE ID

CVE-2026-29791

GHSA ID

GHSA-v2x6-wwfw-r2rq

Source code

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.