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8.1

Deno on Windows: Malicious Batch Files Can Launch Unintended Programs

JLSEC-2026-113
Summary

Deno, a JavaScript runtime, has a security issue on Windows that allows attackers to execute unauthorized programs by manipulating batch files. This can happen if user-input data is not properly validated when running batch scripts. To stay secure, ensure you're running the latest version of Deno and validate any user input before passing it to batch files.

What to do
  • Update deno_jll to version 2.6.3+0.
Affected software
VendorProductAffected versionsFix available
– deno_jll <= 2.6.3+0 2.6.3+0
Original title
Deno is Vulnerable to Command Injection on Windows During Batch File Execution
Original description
### Summary

Deno versions up to 2.5.1 are vulnerable to Command Line Injection attacks on Windows when batch files are executed.

### Details

In Windows, `CreateProcess()` always implicitly spawns `cmd.exe` if a batch file (.bat, .cmd, etc.) is being executed even if the application does not specify it via the command line. This makes Deno vulnerable to a command injection attack on Windows as demonstrated by the two proves-of-concept below.

### PoC

Using `node:child_process` (with the `env` and `run` permissions):

```JS
const { spawn } = require('node:child_process');
const child = spawn('./test.bat', ['&calc.exe']);
```

Using `Deno.Command.spawn()` (with the `run` permission):

```JS
const command = new Deno.Command('./test.bat', {
args: ['&calc.exe'],
});
const child = command.spawn();
```

### Impact

Both of these scripts result in opening calc.exe on Windows, thus allowing a Command Line Injection attack when user-provided arguments are passed if the script being executed by the child process is a batch script.
osv CVSS3.1 8.1
Published: 14 Apr 2026 · Updated: 14 Apr 2026 · First seen: 14 Apr 2026