Stored Cross-Site Scripting in MCP Registry by Model Context Protocol
CVE-2026-44429

5.1MEDIUM

Key Information:

Vendor

Modelcontextprotocol

Status
Registry
Vendor
CVE Published:
14 May 2026

What is CVE-2026-44429?

The MCP Registry is prone to a stored cross-site scripting vulnerability that allows attackers to inject malicious event handlers into the registry homepage. This issue arises from insufficient validation of the 'server.websiteUrl' field in published 'server.json' files. Although the server-side validation checks basic URL structure, it fails to adequately sanitize quotes. Consequently, when the value is included in the HTML output, it can break out of attributes and allow for the execution of arbitrary scripts. Users with publish tokens can exploit this to plant harmful scripts visible to all visitors, making this a significant security risk. This vulnerability has been addressed in MCP Registry version 1.7.7.

Affected Version(s)

registry < 1.7.7

References

https://github.com/modelcontextprotocol/registry/security...
x_refsource_CONFIRM

CVSS V4

Score:
5.1
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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