CVE-2026-49860

Deno: WebSocket API sandbox bypass via missing post-DNS check

Published Jun 23, 2026 CVSS 3.1 · 5.2 Medium EPSS < 1% KEV · Not listed
Description
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, when a WebSocket connection was opened, 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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-83pc-3rw9-qpwj Deno: WebSocket API sandbox bypass via missing post-DNS check
History
Type Values Removed Values Added
First Time appeared Deno
Deno deno
Vendors & Products Deno
Deno deno
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, when a WebSocket connection was opened, 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.
Title Deno: WebSocket API sandbox bypass via missing post-DNS check
Weaknesses CWE-918
References
Metrics cvssV3_1

{'score': 5.2, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jun 23, 2026, 5:37 PM
Reserved
Jun 1, 2026, 10:03 PM
Status
Analyzed
Published
Jun 23, 2026, 6:18 PM
Modified
Oct 25, 2026, 11:10 PM