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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-22864: 0.67% estimated exploitation activity in the next 30 days; percentile 52.13 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 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.

Published by the source

16 Jan 2026, 15:49 UTC

Last modified by the source

28 Aug 2026, 09:52 UTC

Source last checked

26 Oct 2026, 15:43 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-m3c4-prhw-mrx6

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# Patch Next advisory brief: CVE-2026-22864

Advisory: Deno has an incomplete fix for command-injection prevention on Windows — case-insensitive extension bypass
IDs: CVE-2026-22864, GHSA-m3c4-prhw-mrx6
Record: https://patchnext.com/advisories/cve-2026-22864 (revision 1, source checked 26 Oct 2026, 15:43 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: deno 2.5.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io deno: affected < 2.5.6; fixed in 2.5.6

## Suggested inspection (read-only)
- crates.io deno: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on deno.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-m3c4-prhw-mrx6 (GitHub-reviewed advisory GHSA-m3c4-prhw-mrx6 lists affected ranges: crates.io deno >=0 <2.5.6)

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