GHSA-m3c4-prhw-mrx6 Deno has an incomplete fix for command-injection prevention on Windows — case-insensitive extension bypass

• crates.io deno: < 2.5.6 → fixed in 2.5.6

Summary A prior patch aimed to block spawning Windows batch/shell files by returning an error when a spawned path’s extension matched `.bat` or `.cmd`. That check performs a case-sensitive comparison against lowercase literals and therefore can be bypassed when the extension uses alternate casing (for example `.BAT, .Bat`, etc.). POC ```javascript const command = new Deno.Command('./test.BAT', { args: ['&calc.exe'], }); const child = command.spawn(); ``` This causes `calc.exe` to be launched; see the attached screenshot for evidence. Patched in `CVE-2025-61787` — prevents execution of `.bat` and `.cmd` files: Bypass of the patched vulnerability: Impact The script launches calc.exe on Windows, demonstrating that passing user-controlled arguments to a spawned batch script can result in command-line injection. Mitigation Users should update to Deno v2.5.6 or newer.