GHSA-83pc-3rw9-qpwj Deno: WebSocket API sandbox bypass via missing post-DNS check

• crates.io deno: < 2.8.1 → fixed in 2.8.1

Summary When a WebSocket connection was opened, Deno checked the destination hostname against `--deny-net` rules but did not re-check the IP addresses that hostname resolved to. An attacker-controlled script could use a specially crafted domain name that passes the hostname check yet resolves to a denied IP, bypassing the network restriction entirely. Impact Code running under `--deny-net` could connect to hosts that the user intended to block. In practice this means network isolation rules — for example, blocking access to `localhost` or internal services — could be silently circumvented by a malicious or compromised dependency. `Deno.connect` and `fetch()` were not affected by this specific issue (a companion advisory covers `fetch()`). Who is affected Users who: • run untrusted or third-party code with `deno run`, and • rely on `--deny-net` to restrict which hosts that code can reach. If you do not use `--deny-net`, or if you only run fully trusted code, you are not affected. Workaround No workaround is available short of upgrading. If upgrading immediately is not possible, avoid granting `--allow-net` to untrusted code that also has `--deny-net` restrictions you depend on for security.