CVE-2026-49983: 
Rust Analisi e mitigazione delle vulnerabilità

CVE-2026-49983 is a permission bypass vulnerability in Deno's process.loadEnvFile() Node-compatible API that allows a program with only --allow-read permission to mutate process.env, effectively circumventing Deno's --deny-env or --allow-env allowlist restrictions. It affects Deno versions v2.3.0 through v2.8.0 (inclusive) and was first published on May 27, 2026, with the GitHub Advisory Database entry updated on June 16, 2026. The vulnerability carries a CVSS v3.1 base score of 5.2 (Medium) (GitHub Advisory, Deno Advisory).

The root cause is an incorrect authorization check (CWE-863) in Deno's implementation of process.loadEnvFile() from node:process. The function only verifies that the calling program has read permission for the target .env file, but does not check whether the program holds env permission before writing the parsed key-value pairs into process.env. As a result, any program (or third-party dependency it imports) that calls process.loadEnvFile() with a writable or attacker-controlled .env file path — covered by an existing --allow-read grant — can inject arbitrary environment variables into the process, bypassing --deny-env or a restricted --allow-env=FOO,BAR allowlist entirely (GitHub Advisory, Deno Advisory).

Successful exploitation allows an attacker to inject arbitrary environment variables into a Deno process that was explicitly configured to restrict or deny environment access, undermining the integrity of Deno's sandboxing model. The confidentiality impact is low (attacker may read indirectly inferred env state), and the integrity impact is low (environment variables can be overwritten or injected), with no direct availability impact. The scope is marked as Changed because the vulnerability crosses the security boundary of Deno's permission model, potentially affecting components or secrets that depend on environment variable isolation (GitHub Advisory).

1. Identify a vulnerable target: Confirm the target Deno application runs v2.3.0–v2.8.0, uses process.loadEnvFile() (directly or via a dependency), and relies on --deny-env or a restricted --allow-env allowlist as a security boundary.
2. Locate or control the .env file: Identify a .env file path that is (a) covered by the application's --allow-read grant and (b) writable by the attacker or controllable via untrusted input (e.g., a user-writable directory, a third-party dependency that accepts a configurable path).
3. Inject malicious environment variables: Write attacker-controlled key-value pairs into the .env file (e.g., SECRET_KEY=attacker_value or overwriting variables like PATH or NODE_OPTIONS).
4. Trigger process.loadEnvFile(): Cause the application to call process.loadEnvFile() with the attacker-controlled path — this may happen automatically at startup or via a code path that accepts external input.
5. Achieve permission bypass: The injected variables are written into process.env without an env permission check, overriding the intended security boundary and potentially influencing application behavior, leaking secrets, or enabling further exploitation (GitHub Advisory).

• File System: Unexpected or recently modified .env files in directories accessible to the Deno process, particularly in user-writable or world-writable locations.
• Process: Deno processes exhibiting unexpected environment variable values (e.g., overridden PATH, NODE_OPTIONS, or application-specific secrets) inconsistent with the launched configuration.
• Logs: Application logs showing unexpected behavior attributable to changed environment variables (e.g., connecting to different endpoints, using unexpected credentials) after process.loadEnvFile() is called.

Upgrade Deno to version 2.8.1 or later, which contains the fix that enforces env permission checks within process.loadEnvFile(). If an immediate upgrade is not possible, avoid using process.loadEnvFile() in security-sensitive contexts, or ensure that any .env file path accessible to the process cannot be written or controlled by untrusted parties. Additionally, audit third-party dependencies for calls to process.loadEnvFile() from node:process, as the vulnerability can be triggered transitively (GitHub Advisory, Deno Advisory).

The vulnerability was reported by security researcher fallintoplace and published by Deno maintainer bartlomieju on May 27, 2026. No significant broader media coverage or notable community commentary beyond the official advisory has been identified at this time (Deno Advisory).