CVE-2026-125926 · AI agents & MCP
NO FIX YET · SEE WHAT TO DO
The mcp-gateway-registry, an open-source registry and gateway for MCP servers, does not validate the upstream address of a registered server, so a user allowed to register or modify servers can make the gateway send requests to services on the internal network. In some cases the gateway returns those responses to the user.
first public Nov 11, 2026 · 2 sources
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Deployments of mcp-gateway-registry from 1.0.3 through 1.34.0 are exposed, and the flaw requires an account allowed to register or modify servers. Version 1.25.0 fixed a separate issue but does not fix this one, so 1.35.0 or later is needed. If the registry runs with an attached cloud role and logs cannot rule out unexpected activity, review that role's activity and rotate its credentials.
Not affected if auth-required, version-1.35.0-or-later
Who cares aws, lab-disclosure, mcp, python, self-hosted
>= 1.0.3 and <= 1.34.0 are affected.1.35.0 or later.1.35.0 validates upstream addresses on registration and modification but does not change configurations stored before the upgrade; review those manually.CVE-2026-125926 - Server-side request forgery in the server registration and update API in mcp-gateway-registry
Bulletin ID: 2026-180-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 11/11/2026 13:00 PM PST
Description:
mcp-gateway-registry is an open-source registry and gateway for Model Context Protocol (MCP) servers that centralizes discovery, access control, and proxying of registered MCP tool assets. We identified CVE-2026-125926, a server-side request forgery issue in how the registry validates the upstream address of a registered server.
An authenticated user with permission to register or modify a server could configure an upstream address that caused the gateway to send requests to services on the deployment's internal network. In some cases the gateway returned those responses to the user.
Impacted versions: >= v1.0.3 AND <= 1.34.0
Resolution:
This issue has been addressed in mcp-gateway-registry version 1.35.0. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.
Note on version sequencing: a separate and unrelated issue in this product's external management API was addressed in version 1.25.0. A deployment running 1.25.0 or later carries that fix, but remains affected by the issue described here until it runs version 1.35.0 or later.
Post-upgrade actions:
Version 1.35.0 validates server upstream addresses when a server is registered or modified. It leaves server configurations stored before the upgrade unchanged. Customers who ran an affected version should take the following steps after upgrading:
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Workarounds:
The following measures limit risk for deployments that cannot yet upgrade. They do not replace the post-upgrade actions above:
References:
Acknowledgement:
We would like to thank the external researcher (handle novice-22) for collaborating on this issue through the coordinated disclosure process.
Please email aws-security@amazon.com with any s ecurity questions or concerns.
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