---
id: CVE-2026-49983
title: 'Deno is a JavaScript, TypeScript, and WebAssembly runtime'
summary: >-
  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 expectati…
severity: medium
cvss: 5.2
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N'
cwe:
  - CWE-863
published: '2026-06-23'
updated: '2026-06-29'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-49983'
references:
  - url: 'https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv'
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.0014
epssPercentile: 0.03703
ingestedAt: '2026-06-29T13:42:11.981Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.