{"id":"GHSA-cpgj-f7g3-2pp2","revision":"fe38d9a12e06440aa756827bb76ec765","records":[{"revision":"fe38d9a12e06440aa756827bb76ec765","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"GHSA-cpgj-f7g3-2pp2","aliases":["CVE-2026-49859"],"title":"Deno: `fetch()` API sandbox bypass via missing DNS resolution check","description":"## 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.","state":0,"publishedAt":"2026-06-16T19:02:55+00:00","modifiedAt":"2026-07-20T21:15:27.2596988+00:00","affected":[{"ecosystem":"crates.io","name":"deno","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"2.8.1"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/denoland/deno/security/advisories/GHSA-cpgj-f7g3-2pp2","https://nvd.nist.gov/vuln/detail/CVE-2026-49859","https://github.com/denoland/deno"],"sourceUrl":"https://github.com/advisories/GHSA-cpgj-f7g3-2pp2","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-cpgj-f7g3-2pp2","identifiers":["GHSA-cpgj-f7g3-2pp2","CVE-2026-49859"]},"retained":false,"historicalAffected":[]}],"coverage":[]}