Vulnerability · Published Apr 9, 2026 · Assigned by GitHub_M
CVE-2026-35577Missing Host Header Validation in Apollo MCP Server for Localhost Deployments
Medium 6.8
In plain English
A medium-severity security flaw in apollo-mcp-server from apollographql. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities).
Official description
Apollo MCP Server is a Model Context Protocol server that exposes GraphQL operations as MCP tools. Prior to version 1.7.0, the Apollo MCP Server did not validate the Host header on incoming HTTP requests when using StreamableHTTP transport. In configurations where an HTTP-based MCP server is run on localhost without additional authentication or network-level controls, this could potentially allow a malicious website—visited by a user running the server locally—to use DNS rebinding techniques to bypass same-origin policy restrictions and issue requests to the local MCP server. If successfully exploited, this could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the local user. This issue is limited to HTTP-based transport modes (StreamableHTTP). It does not affect servers using stdio transport. The practical risk is further reduced in deployments that use authentication, network-level access controls, or are not bound to localhost. This vulnerability is fixed in 1.7.0.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| apollographql | apollo-mcp-server | < 1.7.0 |
Weakness: CWE-346 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
References
- https://github.com/apollographql/apollo-mcp-server/security/advisories/GHSA-wqrj-vp8w-f8vh x_refsource_CONFIRM
- https://github.com/apollographql/apollo-mcp-server/pull/602 x_refsource_MISC
- https://github.com/apollographql/apollo-mcp-server/pull/635 x_refsource_MISC