What’s Vulnerable › Vulnerabilities
CVE-2026-49859: Deno: `fetch()` API sandbox bypass via missing DNS resolution check
- Severity: medium (CVSS 5.2 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.1% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-06-23 · updated 2026-10-25
- Weakness: CWE-693
Description
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.
Affected products
- denoland deno: before 2.8.1 — fixed in 2.8.1
How to fix
Upgrade to a fixed version: denoland deno 2.8.1. Check the vendor advisory for mitigations.
References
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