CVE-2026-49860
MediumCVSS 5.2Exploitation Probability (EPSS)
Low risk1th percentile - higher than 1% of all known CVEs
Summary
In Deno prior to 2.8.1, when a WebSocket connection was opened, only the destination hostname was checked against --deny-net rules, but the IP addresses that hostname resolved to were not re-checked. 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.
Risk Assessment
The organization is at risk of network security policy bypass, allowing a malicious script to communicate with internal or restricted resources, potentially leading to data exfiltration or further system compromise.
Recommendation
Immediately update Deno to version 2.8.1 or later, which contains the fix for this vulnerability.
Other vulnerabilities in Deno
See all- CVE-2026-22864High
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Before 2.5.6, a prior patch aimed to block spawning Windows batch/shell files by returning an error when a spawned path’s extension matched .bat or .cmd. That check performs a case-sensitive comparison against lowercase literals and therefore can be bypassed when the extension uses alternate casing (for example .BAT, .Bat, etc.). This vulnerability is fixed in 2.5.6.
- CVE-2026-22863High
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Before 2.6.0, node:crypto doesn't finalize cipher. The vulnerability allows an attacker to have infinite encryptions. This can lead to naive attempts at brute forcing, as well as more refined attacks with the goal to learn the server secrets. This vulnerability is fixed in 2.6.0.
- CVE-2026-55517Medium
A vulnerability in Deno before version 2.7.5 allows a remote WebSocket server to crash the Deno process by sending a response with Sec-WebSocket-Protocol or Sec-WebSocket-Extensions headers containing non-printable ASCII bytes (0x80-0xFF). The flaw is due to improper parsing of these headers, causing a panic that terminates the entire process.
- CVE-2026-49983Medium
In Deno prior to 2.8.1, the process.loadEnvFile() function does not honor environment permission restrictions (--deny-env). It allows writing variables from a .env file into the process even when environment access is denied.
- CVE-2026-49859Medium
In Deno prior to version 2.8.1, the fetch() function checked the destination hostname against --deny-net rules but did not re-check the resolved IP addresses. An attacker-controlled script could use a specially crafted domain name that passes the hostname check yet resolves to a denied IP, bypassing network restrictions entirely.
Original NVD description (English source)
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.