CVE-2026-29791 is a medium-severity (CVSS 4.9) Improper Input Validation vulnerability in github.com/agentgateway/agentgateway. A fix is available for github.com/agentgateway/agentgateway — see the affected versions and patch details below.
Agentgateway: Missing parameter sanitization in MCP to OpenAPI conversion
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-29791.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/agentgateway/agentgatewayReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
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!
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/agentgateway/agentgateway | all versions | 0.12.0go get github.com/agentgateway/agentgateway@v0.12.0 |
Affected Products
agentgatewaylfprojectsDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/agentgateway/agentgateway, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/agentgateway/agentgateway to 0.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-29791 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-29791 in your dependencies?
Find it across Go, including transitive dependencies.