CVE-2026-49983

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.

Am I affected?

You are potentially affected if all of the following are true:

1. You run Deno v2.3.0 or newer.
2. Your program (or any dependency it imports) calls process.loadEnvFile()
   from node:process.
3. You rely on Deno's permission model, specifically --deny-env, an
   --allow-env=… allowlist, or running without granting env, as a
   security boundary.
4. The .env path passed to loadEnvFile() can be controlled or modified by
   a less-trusted party (untrusted input, user-writable directory, third-party
   dependency, etc.) and is covered by your --allow-read grant.

If your program does not use process.loadEnvFile() at all, or if it already
grants full env access, this advisory does not change your risk.

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

CVE-2026-49983 has a CVSS score of 5.2 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.8.1); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-49983? CVE-2026-49983 is a medium-severity incorrect authorization vulnerability in deno (rust), affecting versions <= 2.8.0. It is fixed in 2.8.1. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. How severe is CVE-2026-49983? CVE-2026-49983 has a CVSS score of 5.2 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of deno are affected by CVE-2026-49983? deno (rust) versions <= 2.8.0 is affected.
4. Is there a fix for CVE-2026-49983? Yes. CVE-2026-49983 is fixed in 2.8.1. Upgrade to this version or later.
5. Is CVE-2026-49983 exploitable, and should I be worried? Whether CVE-2026-49983 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-49983 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-49983? Upgrade deno to 2.8.1 or later.