mcp-atlassian has an incomplete SSRF remediation

Summary

The UserTokenMiddleware extracts URLs from X-Atlassian-Jira-Url and X-Atlassian-Confluence-Url HTTP headers and passes them directly to API client constructors without any SSRF validation.

Affected Package

• Ecosystem: PyPI
• Package: mcp-atlassian
• Affected versions: all versions before fix commit 5cd697dfce91
• Patched versions: >= commit 5cd697dfce91

Details

In main.py, _process_authentication_headers() extracts URLs from ASGI headers without validation. In dependencies.py, get_jira_fetcher() creates JiraConfig with url=jira_url_header directly. There is no validate_url call, no IP range check, no hostname validation.

The fix adds URL validation to some paths but the header-based URL extraction in _process_authentication_headers() still passes raw URLs through. The derived config objects use the header URL directly and the fetcher makes HTTP requests to that URL.

PoC

jira_url_header = headers.get(b"x-atlassian-jira-url")
jira_url_str = jira_url_header.decode("latin-1") if jira_url_header else None
service_headers["X-Atlassian-Jira-Url"] = jira_url_str

Steps to reproduce:

1. git clone https://github.com/sooperset/mcp-atlassian /tmp/mcp-atlassian_test
2. cd /tmp/mcp-atlassian_test && git checkout 5cd697dfce91~1
3. pip install -e .
4. python3 poc.py

Expected output:

VULNERABILITY CONFIRMED
User-supplied URLs from HTTP headers passed directly to JiraConfig/JiraFetcher with no SSRF validation

Impact

An attacker can set X-Atlassian-Jira-Url: http://169.254.169.254/latest/meta-data/ to access AWS instance metadata, or target any internal service. The server makes authenticated HTTP requests to the attacker-specified URL.

Suggested Remediation

Validate all user-supplied URLs against an allowlist of permitted hostnames or reject private/loopback/link-local IP ranges. Consider requiring server-side configuration of allowed Atlassian instance URLs.