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MEDIUM · 5.2

CVE-2026-49983

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 wi...

Vulnerability 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.

CVSS Score

5.2

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE

Affected Products

VendorProductVersions
DenoDeno>= 2.3.0, < 2.8.1

Related Weaknesses (CWE)

CWE-863

References

FAQ

What is CVE-2026-49983?

CVE-2026-49983 is a vulnerability with a CVSS score of 5.2 (MEDIUM). 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 wi...

How severe is CVE-2026-49983?

CVE-2026-49983 has been rated MEDIUM with a CVSS base score of 5.2/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-49983?

Check the references section above for vendor advisories and patch information. Affected products include: Deno Deno.