What’s Vulnerable › Vulnerabilities

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

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-01-15 · updated 2026-06-17
• Weakness: CWE-77

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.

Affected products

• denoland deno: before 2.5.6 — fixed in 2.5.6

How to fix

Upgrade to a fixed version: denoland deno 2.5.6. Check the vendor advisory for mitigations.

References

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

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