CVE-2026-22864
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.).
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.68%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.68% probability · 51th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-77
- Affected
- deno/deno
- Source
- security-advisories@github.com
References
- https://github.com/denoland/deno/releases/tag/v2.5.6Release Notes
- https://github.com/denoland/deno/security/advisories/GHSA-m3c4-prhw-mrx6Exploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.