5.2

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-49983

CVE-2026-49983: Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access

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.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-49983

CVE-2026-49983:

5.2

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

SSVC / BOD 26-04 ↗

Exploitation NoneAutomatable NoTech Impact Partial

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Package Name	Ecosystem	Vulnerable Versions	First Patched Version
deno	rust	<= 2.8.0	2.8.1

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability, as described in the advisory, allows bypassing Deno's environment permission checks using the process.loadEnvFile() function. The advisory states that versions up to 2.8.0 are vulnerable, and 2.8.1 is patched. By comparing the git tags for v2.8.0 and v2.8.1, I identified the fixing commit 044bed8486dbc64ef486fbee214d9ecf40cac41b. The commit message, "fix(ext/node): require env permission for process.loadEnvFile", directly points to the vulnerability. The code changes are in the Rust file ext/node/lib.rs, specifically within the function op_node_load_env_file. The patch introduces a call to permissions.check_env_all(), which was previously missing. This confirms that op_node_load_env_file is the vulnerable function, as it was responsible for loading the environment variables without proper authorization checks.

Vulnerable functions

op_node_load_env_file

ext/node/lib.rs

This Rust function is the underlying implementation for the `process.loadEnvFile()` JavaScript API. The vulnerability existed because this function did not check for environment permissions (`--allow-env`) before reading the specified `.env` file and setting the environment variables. It only performed a file read permission check. This allowed a program with only file read access to modify the process environment, bypassing Deno's security sandbox. The patch adds a call to `check_env_all()` to ensure the necessary environment permissions are granted before proceeding.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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