CVE-2026-77265

## Summary The SSRF protection for header-based authentication uses a validate-then-use pattern vulnerable to DNS rebinding. validate_url_for_ssrf resolves the hostname via DNS and checks that the resolved IP is globally routable. However, the actual HTTP request happens later, during which the DNS record may have changed to point to an internal IP (127.0.0.1, 169.254.169.254, etc.). The SSRF redirect hook only validates redirect targets, not the initial connection. ## Details The vulnerability spans main.py (validation) and dependencies.py (use). **Step 1 -- URL validation at middleware time:** In src/mcp_atlassian/servers/main.py:524-531, the URL from X-Atlassian-Jira-Url is validated: if jira_url_str: ssrf_error = validate_url_for_ssrf(jira_url_str) if ssrf_error: # blocked validate_url_for_ssrf (src/mcp_atlassian/utils/urls.py:113-116) resolves DNS and checks is_global: dns_error = _check_dns_resolution(hostname) if dns_error: return dns_error **Step 2 -- HTTP request happens later with a separate DNS resolution:** In src/mcp_atlassian/servers/dependencies.py:544-562, a JiraFetcher is created with the attacker URL and makes HTTP requests to it. The SSRF redirect hook (attach_ssrf_hook=True) is applied but only checks redirect Location headers, not the initial connection target. **DNS rebinding timeline:** 1. Attacker sets up rebind.attacker.com with short TTL (1 second) 2. First DNS resolution (validate_url_for_ssrf): returns 1.2.3.4 (public) -- passes 3. TTL expires 4. Second DNS resolution (requests.get): returns 169.254.169.254 (metadata) 5. HTTP request reaches internal IP, bypassing the SSRF check ## PoC Use a DNS rebinding service like rbndr.us. Send a request with X-Atlassian-Jira-Url set to a rebinding hostname (e.g., rebind-169.254.169.254-1.2.3.4.rbndr.us) and X-Atlassian-Jira-Personal-Token set to any value. With approximately 50% probability per attempt, the request reaches the internal me