GHSA-4C8G-JVCX-V4HV

Vulnerability from github – Published: 2026-06-16 19:04 – Updated: 2026-06-16 19:04
VLAI
Summary
Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access
Details

Summary

In Deno, 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.

Am I affected?

You are potentially affected if all of the following are true:

  1. You run Deno v2.3.0 or newer.
  2. Your program (or any dependency it imports) calls process.loadEnvFile() from node:process.
  3. You rely on Deno's permission model — specifically --deny-env, an --allow-env=… allowlist, or running without granting env — as a security boundary.
  4. The .env path passed to loadEnvFile() can be controlled or modified by a less-trusted party (untrusted input, user-writable directory, third-party dependency, etc.) and is covered by your --allow-read grant.

If your program does not use process.loadEnvFile() at all, or if it already grants full env access, this advisory does not change your risk.

Severity
5.2 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.8.0"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "deno"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.8.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-49983"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-16T19:04:57Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nIn Deno, environment access is gated by the `env` permission. You can deny it\nwith `--deny-env`, or restrict it to a specific allowlist with\n`--allow-env=FOO,BAR`. The expectation is that a program running without `env`\npermission cannot change `process.env`.\n\n`process.loadEnvFile()` (the Node-compatible API for loading variables from a\n`.env` file) does **not** honor this. It only checks that the program has\n**read** permission for the dotenv file, then writes every key in that file\ninto the process environment \u2014 even when `env` access is denied.\n\nIn effect, **`--allow-read` plus a writable or attacker-controlled `.env` file\nis enough to defeat `--deny-env`.**\n\n## Am I affected?\n\nYou are potentially affected if **all** of the following are true:\n\n1. You run Deno **v2.3.0 or newer**.\n2. Your program (or any dependency it imports) calls `process.loadEnvFile()`\n   from `node:process`.\n3. You rely on Deno\u0027s permission model \u2014 specifically `--deny-env`, an\n   `--allow-env=\u2026` allowlist, or running without granting `env` \u2014 as a\n   security boundary.\n4. The `.env` path passed to `loadEnvFile()` can be controlled or modified by\n   a less-trusted party (untrusted input, user-writable directory, third-party\n   dependency, etc.) and is covered by your `--allow-read` grant.\n\nIf your program does not use `process.loadEnvFile()` at all, or if it already\ngrants full `env` access, this advisory does not change your risk.",
  "id": "GHSA-4c8g-jvcx-v4hv",
  "modified": "2026-06-16T19:04:57Z",
  "published": "2026-06-16T19:04:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/denoland/deno"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access"
}


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