JLSEC-2026-1164

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Source
https://github.com/JuliaLang/SecurityAdvisories.jl/blob/main/advisories/published/2026/JLSEC-2026-1164.md
Import Source
https://github.com/JuliaLang/SecurityAdvisories.jl/tree/generated/osv/2026/JLSEC-2026-1164.json
JSON Data
https://api.osv.dev/v1/vulns/JLSEC-2026-1164
Upstream
  • EUVD-2026-38541
Published
2026-08-05T18:20:40.259Z
Modified
2026-08-05T18:37:02.708842313Z
Severity
  • 5.2 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N CVSS Calculator
Summary
Deno: `fetch()` API sandbox bypass via missing DNS resolution check
Details

Summary

When fetch() was called, 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 reach 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.

A companion advisory covers the same class of issue in the WebSocket API.

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.

Fix

The fetch() DNS resolver now performs a post-resolution check on every IP address before passing it to the HTTP connector, consistent with how Deno.connect already behaved.

Database specific 
{
    "license": "CC-BY-4.0",
    "sources": [
        {
            "database_specific": {
                "status": "Analyzed"
            },
            "modified": "2026-06-29T14:38:17.253Z",
            "id": "CVE-2026-49859",
            "published": "2026-06-23T18:18:03.927Z",
            "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-49859",
            "imported": "2026-08-05T06:30:31.265Z",
            "html_url": "https://nvd.nist.gov/vuln/detail/CVE-2026-49859"
        },
        {
            "modified": "2026-07-20T21:01:14Z",
            "url": "https://api.github.com/advisories/GHSA-cpgj-f7g3-2pp2",
            "published": "2026-06-16T19:02:55Z",
            "id": "GHSA-cpgj-f7g3-2pp2",
            "imported": "2026-08-05T06:30:41.504Z",
            "html_url": "https://github.com/advisories/GHSA-cpgj-f7g3-2pp2"
        },
        {
            "html_url": "https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-38541",
            "id": "EUVD-2026-38541",
            "published": "2026-06-23T17:14:16Z",
            "url": "https://euvdservices.enisa.europa.eu/api/enisaid?id=EUVD-2026-38541",
            "imported": "2026-08-05T06:30:31.318Z",
            "modified": "2026-06-24T14:23:09Z"
        }
    ]
}
References
Credits

Affected packages

Julia / Deno_jll

Package

Name
Deno_jll
Purl
pkg:julia/Deno_jll?uuid=04572ae6-984a-583e-9378-9577a1c2574d

Affected ranges

Type
SEMVER
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
2.8.1+0

Database specific

source 
"https://github.com/JuliaLang/SecurityAdvisories.jl/tree/generated/osv/2026/JLSEC-2026-1164.json"