CVE-2026-49983
Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access
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.
INFO
Published Date :
June 23, 2026, 6:18 p.m.
Last Modified :
Oct. 25, 2026, 11:10 p.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | MITRE-CVE | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Deno to version 2.8.1 or later.
- Review and restrict environment variable access.
- Validate .env file access controls.
Public PoC/Exploit Available at Github
CVE-2026-49983 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-49983.
| URL | Resource |
|---|---|
| https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-49983 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-49983
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
None
Rust Java JavaScript TypeScript
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-49983 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-49983 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 25, 2026
Action Type Old Value New Value Added Translation Title: deno de denoland, Description: Deno es un entorno de ejecución de JavaScript, TypeScript y WebAssembly. Antes de la versión 2.8.1, el acceso al entorno está controlado por el permiso env. Se puede denegar con --deny-env, o restringirlo a una lista de permitidos específica con --allow-env=FOO,BAR. La expectativa es que un programa que se ejecuta sin el permiso env no pueda cambiar process.env. process.loadEnvFile() (la API compatible con Node para cargar variables de un archivo .env) no respeta esto. Solo verifica que el programa tenga permiso de lectura para el archivo dotenv, luego escribe cada clave de ese archivo en el entorno del proceso, incluso cuando el acceso env está denegado. En efecto, --allow-read más un archivo .env escribible o controlado por el atacante es suficiente para eludir --deny-env. Esta vulnerabilidad está corregida en la versión 2.8.1. -
Initial Analysis by [email protected]
Jun. 29, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:deno:deno:*:*:*:*:*:*:*:* versions from (including) 2.3.0 up to (excluding) 2.8.1 Added Reference Type GitHub, Inc.: https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv Types: Vendor Advisory -
New CVE Received by [email protected]
Jun. 23, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'denoland', 'product': 'deno', 'versions': [{'status': 'affected', 'version': '< 2.8.1'}]}] Added 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. Added CVSS V3.1 AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N Added CWE CWE-863 Added Reference https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 23, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-49983', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-23T17:54:45.354967Z'}