High severityOSV Advisory· Published Jan 15, 2026· Updated Jan 16, 2026
Deno has an incomplete fix for command-injection prevention on Windows — case-insensitive extension bypass
CVE-2026-22864
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.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
denocrates.io | < 2.5.6 | 2.5.6 |
Affected products
2Patches
Vulnerability mechanics
References
4- github.com/advisories/GHSA-m3c4-prhw-mrx6ghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-22864ghsaADVISORY
- github.com/denoland/deno/releases/tag/v2.5.6ghsax_refsource_MISCWEB
- github.com/denoland/deno/security/advisories/GHSA-m3c4-prhw-mrx6ghsax_refsource_CONFIRMWEB
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