{"id":"JLSEC-2026-1165","summary":"Deno: WebSocket API sandbox bypass via missing post-DNS check","details":"## Summary\n\nWhen a WebSocket connection was opened, Deno checked the destination hostname\nagainst `--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 connect to hosts that the user intended\nto block. In practice this means network isolation rules — for example,\nblocking access to `localhost` or internal services — could be silently\ncircumvented by a malicious or compromised dependency.\n\n`Deno.connect` and `fetch()` were not affected by this specific issue (a\ncompanion advisory covers `fetch()`).\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.","modified":"2026-08-05T18:29:10.840910181Z","published":"2026-08-05T18:20:40.259Z","upstream":["CVE-2026-49860","EUVD-2026-38542","GHSA-83pc-3rw9-qpwj"],"database_specific":{"sources":[{"database_specific":{"status":"Analyzed"},"id":"CVE-2026-49860","imported":"2026-08-05T06:30:31.282Z","modified":"2026-06-29T14:37:08.490Z","published":"2026-06-23T18:18:04.053Z","url":"https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-49860","html_url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49860"},{"html_url":"https://github.com/advisories/GHSA-83pc-3rw9-qpwj","id":"GHSA-83pc-3rw9-qpwj","imported":"2026-08-05T06:30:32.446Z","modified":"2026-07-20T21:01:05Z","published":"2026-06-16T19:04:07Z","url":"https://api.github.com/advisories/GHSA-83pc-3rw9-qpwj"},{"id":"EUVD-2026-38542","imported":"2026-08-05T06:30:31.318Z","modified":"2026-06-23T17:37:07Z","published":"2026-06-23T17:15:05Z","url":"https://euvdservices.enisa.europa.eu/api/enisaid?id=EUVD-2026-38542","html_url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-38542"}],"license":"CC-BY-4.0"},"references":[{"type":"WEB","url":"https://github.com/advisories/GHSA-83pc-3rw9-qpwj"},{"type":"WEB","url":"https://github.com/denoland/deno/security/advisories/GHSA-83pc-3rw9-qpwj"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49860"}],"affected":[{"package":{"name":"Deno_jll","ecosystem":"Julia","purl":"pkg:julia/Deno_jll?uuid=04572ae6-984a-583e-9378-9577a1c2574d"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.8.1+0"}]}],"database_specific":{"source":"https://github.com/JuliaLang/SecurityAdvisories.jl/tree/generated/osv/2026/JLSEC-2026-1165.json"}}],"schema_version":"1.8.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N","source":"CNA"}],"credits":[{"name":"alcls01111","contact":["https://github.com/alcls01111"],"type":"REPORTER"}]}