Missing Host Header Validation in Apollo MCP Server for Localhost Deployments

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Summary

CVECVE-2026-35577
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-09 20:16:25 UTC
Updated2026-04-13 15:02:27 UTC
DescriptionApollo 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.

Risk And Classification

Primary CVSS: v3.1 6.8 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

EPSS: 0.000170000 probability, percentile 0.041320000 (date 2026-04-13)

Problem Types: CWE-346 | CWE-346 CWE-346: Origin Validation Error

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
3.1CNADECLARED6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Apollographql Apollo-mcp-server affected < 1.7.0 Not specified

References

ReferenceSourceLinkTags
github.com/apollographql/apollo-mcp-server/pull/602 [email protected] github.com
github.com/apollographql/apollo-mcp-server/pull/635 [email protected] github.com
github.com/apollographql/apollo-mcp-server/security/advisories/GHSA-wqrj... [email protected] github.com
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