CVE-2026-49983 Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access
Attackers can bypass environment variable permission restrictions in Deno by using process.loadEnvFile() with read access to a .env file.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-49983?
CVE-2026-49983 is a medium-severity vulnerability in denoland deno, published on 23 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-863
Which versions are affected by CVE-2026-49983?
2 open source packages ship an affected version, including deno. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
deno crates.io | All versions | 2.8.1 |
deno crates.io | All versions | 2.8.1 |
Products include Deno Deno.
How do I fix CVE-2026-49983?
Upgrade deno to 2.8.1 or later.
Is CVE-2026-49983 being exploited?
There is no known exploitation of CVE-2026-49983 in the wild and no public exploit code.
Other vulnerabilities in denoland deno
- CVE-2023-28445 Deno improperly handles resizable ArrayBuffer
- CVE-2022-24783 Sandbox bypass leading to arbitrary code execution in Deno
- CVE-2021-32619 Static imports inside dynamically imported modules do not adhere to permission checks
- CVE-2026-22863 Deno node:crypto doesn't finalize cipher
- CVE-2024-27936 Deno interactive permission prompt spoofing via improper ANSI stripping
Sources
Also known as GHSA-4c8g-jvcx-v4hv, JLSEC-2026-1166.