What’s Vulnerable › Vulnerabilities
CVE-2026-49983: Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access
- 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-863
Description
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, environment access is gated by the env permission. You can deny it with --deny-env, or restrict it to a specific allowlist with --allow-env=FOO,BAR. The expectation is that a program running without env permission cannot change process.env. process.loadEnvFile() (the Node-compatible API for loading variables from a .env file) does not honor this. It only checks that the program has read permission for the dotenv file, then writes every key in that file into the process environment — even when env access is denied. In effect, --allow-read plus a writable or attacker-controlled .env file is enough to defeat --deny-env. This vulnerability is fixed in 2.8.1.
Affected products
- denoland deno: from 2.3.0 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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