Medium
Deno: `fetch()` API sandbox bypass via missing DNS resolution check
Type: advisorySources: OSV
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, 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. This vulnerability is fixed in 2.8.1.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-49859
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 07:59 UTC · Revision 1
Source evidence
Deno: `fetch()` API sandbox bypass via missing DNS resolution check
core-osv · Original sourcePublished 23 Jun 2026, 17:14 UTC
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, 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. This vulnerability is fixed in 2.8.1.
osv:CVE-2026-49859
Complete source record
{
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"url": "https://osv.dev/vulnerability/CVE-2026-49859",
"method": "structured",
"payload": {
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"title": "Deno: `fetch()` API sandbox bypass via missing DNS resolution check",
"summary": "Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, 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. This vulnerability is fixed in 2.8.1.",
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"modified": "2026-10-28T02:30:26.902548051Z",
"provider": "osv",
"references": [
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"source_id": "core-osv",
"document_id": 493566,
"published_at": "2026-06-23T17:14:16.888+00:00"
}