CVE-2026-22864
Deno has an incomplete fix for command-injection prevention on Windows — case-insensitive extension bypass
Summary
### 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.
Affected packages
| Ecosystem | Package | Affected versions | Fixed versions |
|---|---|---|---|
| rust | deno | — | 2.5.6 |
Remediation: Upgrade to 2.5.6 or later.
References
Includes data from the GitHub Advisory Database, licensed under CC-BY 4.0.
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EPSS scores provided by the FIRST.org Exploit Prediction Scoring System.