GHSA-M3C4-PRHW-MRX6

Vulnerability from github – Published: 2026-01-16 15:49 – Updated: 2026-01-16 15:49
VLAI?
Summary
Deno has an incomplete fix for command-injection prevention on Windows — case-insensitive extension bypass
Details

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

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: photo_2025-10-10 02 27 23

Bypass of the patched vulnerability: photo_2025-10-10 02 27 25

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.

Severity ?
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "deno"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.5.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-22864"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-77"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-16T15:49:38Z",
    "nvd_published_at": "2026-01-15T23:15:51Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nA prior patch aimed to block spawning Windows batch/shell files by returning an error when a spawned path\u2019s 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.).\n\n### POC\n```javascript\nconst command = new Deno.Command(\u0027./test.BAT\u0027, {\n  args: [\u0027\u0026calc.exe\u0027],\n});\nconst child = command.spawn();\n```\nThis causes `calc.exe` to be launched; see the attached screenshot for evidence.\n\n**Patched in `CVE-2025-61787` \u2014 prevents execution of `.bat` and `.cmd` files:**\n![photo_2025-10-10 02 27 23](https://github.com/user-attachments/assets/43df25e2-e2e1-48aa-8060-cb0a22637f1f)\n\n**Bypass of the patched vulnerability:**\n![photo_2025-10-10 02 27 25](https://github.com/user-attachments/assets/2be1afb4-84a1-4883-8e18-6a174fdd3615)\n\n\n### Impact\nThe script launches calc.exe on Windows, demonstrating that passing user-controlled arguments to a spawned batch script can result in command-line injection.\n\n### Mitigation\n\nUsers should update to Deno v2.5.6 or newer.",
  "id": "GHSA-m3c4-prhw-mrx6",
  "modified": "2026-01-16T15:49:38Z",
  "published": "2026-01-16T15:49:38Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/denoland/deno/security/advisories/GHSA-m3c4-prhw-mrx6"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-22864"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/denoland/deno"
    },
    {
      "type": "WEB",
      "url": "https://github.com/denoland/deno/releases/tag/v2.5.6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Deno has an incomplete fix for command-injection prevention on Windows \u2014 case-insensitive extension bypass"
}


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