# CVE-2026-44429: MCP Registry stored XSS in catalogue UI via websiteUrl

Source: https://junglewise.ai/threats/cve-2026-44429-mcp-registry-stored-xss-in-catalogue-ui-via-websiteurl  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-14. Updated: 2026-05-16  
License: CC BY 4.0 with a link back

CVE-2026-44429 · Severity: medium · CVSS 5.4 · Published 2026-05-14

The Model Context Protocol (MCP) Registry is a directory for AI-related server components. A vulnerability in the registry's web interface allows malicious publishers to inject malicious scripts into the catalogue. If a user views a poisoned entry, the attacker could steal authentication tokens, redirect the user to malicious sites, or perform actions on the user's behalf within the registry.

Technologies: [github.com/modelcontextprotocol/registry (Go)](https://junglewise.ai/threats/technologies/github-com-modelcontextprotocol-registry), [Model Context Protocol Registry](https://junglewise.ai/threats/technologies/registry). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Model Context Protocol](https://junglewise.ai/threats/vendors/model-context-protocol).

## Quick answers

**Is CVE-2026-44429 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-44429 being exploited in the wild.

**How severe is CVE-2026-44429?** Medium severity, with a CVSS score of 5.4, published 14 May 2026.

**Which products and versions are affected?** github.com/modelcontextprotocol/registry (Go) < 1.7.7, SEMVER:introduced=0,fixed=1.7.7; Model Context Protocol Registry < 1.7.7; Model Context Protocol Registry < 1.7.7.

**Is there a fix for CVE-2026-44429?** Yes. github.com/modelcontextprotocol/registry (Go): upgrade to 1.7.7 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-44429 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-44429?** Check whether you run github.com/modelcontextprotocol/registry (Go), Model Context Protocol Registry or Model Context Protocol Registry at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/modelcontextprotocol/registry (Go): upgrade to 1.7.7 or later

  ```sh
  go get github.com/modelcontextprotocol/registry@v1.7.7
  ```


## Technical details

A stored cross-site scripting (XSS) vulnerability exists in the MCP Registry catalogue UI due to improper output encoding of the `websiteUrl` field. While the application uses a homegrown `escapeHtml` helper, this helper only sanitizes characters for text content (like `<` and `&`) and fails to escape double quotes (`"`). An attacker with publishing privileges can provide a URL containing a double quote to break out of the `href` attribute in the `ui_index.html` template. This allows the injection of arbitrary HTML attributes, such as `onmouseover`, which execute JavaScript when a user interacts with the malicious entry. The existing Content Security Policy (CSP) fails to mitigate this because it includes `'unsafe-inline'`. The issue is fixed in version 1.7.7 by improving validation and encoding.

## Affected products

- modelcontextprotocol registry < 1.7.7

## Identifiers

- CVE-2026-44429
- GHSA-rqv2-m695-f8j4
- GO-2026-5637

## Timeline

- 2026-05-04: disclosed: Vulnerability reported to vendor
- 2026-05-08: advisory: GitHub Advisory published
- 2026-05-08: patched: Fix released in version 1.7.7

## References

- [https://api.github.com/users/JosephDoUrden](https://api.github.com/users/JosephDoUrden)
- [https://github.com/JosephDoUrden](https://github.com/JosephDoUrden)
- [https://api.github.com/users/JosephDoUrden/gists%7B/gist_id%7D](https://api.github.com/users/JosephDoUrden/gists%7B/gist_id%7D)
- [https://api.github.com/users/JosephDoUrden/repos](https://api.github.com/users/JosephDoUrden/repos)
- [https://avatars.githubusercontent.com/u/67666222?v=4](https://avatars.githubusercontent.com/u/67666222?v=4)
- [https://api.github.com/users/JosephDoUrden/events%7B/privacy%7D](https://api.github.com/users/JosephDoUrden/events%7B/privacy%7D)

## Related threats

- [Model Context Protocol Registry OIDC token replay via shared audience](https://junglewise.ai/threats/cve-2026-44428-model-context-protocol-registry-oidc-token-replay-via-shared)
- [Model Context Protocol Registry open redirect in TrailingSlashMiddleware](https://junglewise.ai/threats/cve-2026-44427-model-context-protocol-registry-open-redirect-in)
- [Model Context Protocol Registry ownership bypass in OCI validator](https://junglewise.ai/threats/cve-2026-45781-model-context-protocol-registry-ownership-bypass-in-oci-validator)
- [Model Context Protocol Registry SSRF via IPv6 Filter Bypass](https://junglewise.ai/threats/cve-2026-44430-model-context-protocol-registry-ssrf-via-ipv6-filter-bypass)