Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.2 · CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-49983: 0.14% estimated exploitation activity in the next 30 days; percentile 3.35 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.…

Published by the source

16 Jun 2026, 19:04 UTC

Last modified by the source

20 Jul 2026, 21:01 UTC

Source last checked

26 Oct 2026, 15:43 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-4c8g-jvcx-v4hv

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# Patch Next advisory brief: CVE-2026-49983

Advisory: Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access
IDs: CVE-2026-49983, GHSA-4c8g-jvcx-v4hv
Record: https://patchnext.com/advisories/cve-2026-49983 (revision 1, source checked 26 Oct 2026, 15:43 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: deno 2.8.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io deno: affected <= 2.8.0; fixed in 2.8.1

## Suggested inspection (read-only)
- crates.io deno: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on deno.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-4c8g-jvcx-v4hv (GitHub-reviewed advisory GHSA-4c8g-jvcx-v4hv lists affected ranges: crates.io deno >=0 <=2.8.0)

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