Agentgateway is missing parameter sanitization in MCP to OpenAPI conversion

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.9 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-29791: 0.17% estimated exploitation activity in the next 30 days; percentile 6.05 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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!

Published by the source

5 Mar 2026, 01:02 UTC

Last modified by the source

6 Mar 2026, 22:51 UTC

Source last checked

26 Oct 2026, 15:15 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-v2x6-wwfw-r2rq

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# Patch Next advisory brief: CVE-2026-29791

Advisory: Agentgateway is missing parameter sanitization in MCP to OpenAPI conversion
IDs: CVE-2026-29791, GHSA-v2x6-wwfw-r2rq
Record: https://patchnext.com/advisories/cve-2026-29791 (revision 1, source checked 26 Oct 2026, 15:15 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/agentgateway/agentgateway 0.12.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/agentgateway/agentgateway: affected < 0.12.0; fixed in 0.12.0

## Suggested inspection (read-only)
- Go github.com/agentgateway/agentgateway: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/agentgateway/agentgateway.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-v2x6-wwfw-r2rq (GitHub-reviewed advisory GHSA-v2x6-wwfw-r2rq lists affected ranges: Go github.com/agentgateway/agentgateway >=0 <0.12.0)

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