Deno: `fetch()` API sandbox bypass via missing DNS resolution check

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Summary

CVECVE-2026-49859
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-23 18:18:03 UTC
Updated2026-06-23 19:34:58 UTC
DescriptionDeno 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.

Risk And Classification

Primary CVSS: v3.1 5.2 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

Problem Types: CWE-693 | CWE-918 | CWE-693 CWE-693: Protection Mechanism Failure | CWE-918 CWE-918: Server-Side Request Forgery (SSRF)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.2MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
3.1CNADECLARED5.2MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Denoland Deno affected < 2.8.1 Not specified

References

ReferenceSourceLinkTags
github.com/denoland/deno/security/advisories/GHSA-cpgj-f7g3-2pp2 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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