Prefect CVE-2026-7724

The vulnerability exists in the webhook and notification components' URL validation logic (CWE-367: Improper Synchronization). The validate_restricted_url function performs initial DNS resolution and IP validation to prevent SSRF attacks targeting private addresses, but this validation occurs before the actual HTTP connection is established. An attacker can exploit the time gap between validation and connection by performing DNS rebinding: the hostname initially resolves to a public IP (passing validation), then resolves to a private IP (like 127.0.0.1 or 10.0.0.0/8) when the HTTP client actually establishes the connection. The fix implements SSRFProtectedAsyncHTTPTransport and SSRFProtectedHTTPTransport that re-validate the resolved IP at connection time and pin the connection to the pre-resolved address, eliminating the TOCTOU window. The patch also upgrades from socket.gethostbyname (which returns only the first A record) to socket.getaddrinfo (which validates all resolved addresses), closing an additional bypass where a hostname publishes both public and private records.