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

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.