GHSA-489G-7RXV-6C8Q MCP Atlassian: DNS-rebinding TOCTOU bypass of the SSRF fix (CVE-2026-27826)

Summary GHSA-7r34-79r5-rcc9's fix added validateurlforssrf, which resolves the attacker-controlled X-Atlassian-Jira,Confluence-Url header host once at middleware time and trusts the result. But the outbound request is later built with the raw hostname and re-resolves at connect time with no IP...