CVE-2026-49983 Details
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.
A vulnerability in Deno versions through 2.8.0 allows the process.loadEnvFile() function to bypass environment permission checks. The env permission can be denied or restricted to a specific allowlist, with the expectation that programs without env access cannot modify process.env. However, process.loadEnvFile() does not adhere to this restriction. Instead, it only verifies that the program has read permission for the dotenv file, then imports all variables from the file into the process environment, even when env access is denied. This creates a security risk, as granting read access to a writable or attacker-controlled .env file can undermine the denial of env permission.
Users can upgrade to Deno version 2.8.1 or later to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 23, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-863 | Incorrect Authorization | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| deno deno | >= 2.3.0, < 2.8.1 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 29, 2026 | Initial Analysis | [email protected] |
| Jun 23, 2026 | New CVE Received | [email protected] |
| Jun 23, 2026 | CVE Modified | CISA-ADP |