CVE-2026-22864

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:

Bypass of the patched vulnerability:

Mitigation

Users should update to Deno v2.5.6 or newer.

The script launches calc.exe on Windows, demonstrating that passing user-controlled arguments to a spawned batch script can result in command-line injection.

Untrusted input is inserted into a command that is later executed by the application, allowing the attacker to alter the intent of that command. Typical impact: arbitrary command execution in the application's environment.

CVE-2026-22864 has a CVSS score of 8.1 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.5.6); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-22864? CVE-2026-22864 is a high-severity command injection vulnerability in deno (rust), affecting versions < 2.5.6. It is fixed in 2.5.6. Untrusted input is inserted into a command that is later executed by the application, allowing the attacker to alter the intent of that command.
2. How severe is CVE-2026-22864? CVE-2026-22864 has a CVSS score of 8.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of deno are affected by CVE-2026-22864? deno (rust) versions < 2.5.6 is affected.
4. Is there a fix for CVE-2026-22864? Yes. CVE-2026-22864 is fixed in 2.5.6. Upgrade to this version or later.
5. Is CVE-2026-22864 exploitable, and should I be worried? Whether CVE-2026-22864 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-22864 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-22864? Upgrade deno to 2.5.6 or later.