{"id":"GHSA-cpgj-f7g3-2pp2","summary":"Deno: `fetch()` API sandbox bypass via missing DNS resolution check","details":"## Summary\n\nWhen `fetch()` was called, Deno checked the destination hostname against\n`--deny-net` rules but did not re-check the IP addresses that hostname\nresolved to. An attacker-controlled script could use a specially crafted domain\nname that passes the hostname check yet resolves to a denied IP, bypassing the\nnetwork restriction entirely.\n\n## Impact\n\nCode running under `--deny-net` could reach hosts that the user intended to\nblock. In practice this means network isolation rules — for example, blocking\naccess to `localhost` or internal services — could be silently circumvented by\na malicious or compromised dependency.\n\nA companion advisory covers the same class of issue in the WebSocket API.\n\n## Who is affected\n\nUsers who:\n\n- run untrusted or third-party code with `deno run`, and\n- rely on `--deny-net` to restrict which hosts that code can reach.\n\nIf you do not use `--deny-net`, or if you only run fully trusted code, you are\nnot affected.\n\n## Workaround\n\nNo workaround is available short of upgrading. If upgrading immediately is not\npossible, avoid granting `--allow-net` to untrusted code that also has\n`--deny-net` restrictions you depend on for security.\n\n## Fix\n\nThe `fetch()` DNS resolver now performs a post-resolution check on every IP\naddress before passing it to the HTTP connector, consistent with how\n`Deno.connect` already behaved.","aliases":["CVE-2026-49859"],"modified":"2026-07-20T21:15:27.259698816Z","published":"2026-06-16T19:02:55Z","database_specific":{"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-06-16T19:02:55Z","nvd_published_at":"2026-06-23T18:18:03Z","cwe_ids":["CWE-693","CWE-918"]},"references":[{"type":"WEB","url":"https://github.com/denoland/deno/security/advisories/GHSA-cpgj-f7g3-2pp2"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49859"},{"type":"PACKAGE","url":"https://github.com/denoland/deno"}],"affected":[{"package":{"name":"deno","ecosystem":"crates.io","purl":"pkg:cargo/deno"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.8.1"}]}],"database_specific":{"last_known_affected_version_range":"\u003c= 2.8.0","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-cpgj-f7g3-2pp2/GHSA-cpgj-f7g3-2pp2.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N"}]}