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[Security] Path validation bypass on Windows via NTFS Alternate Data Streams (ADS) in secure-filesystem-server #4523

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[Security] Path validation bypass on Windows via NTFS Alternate Data Streams (ADS) in secure-filesystem-server #4523

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12 changes: 12 additions & 0 deletions src/filesystem/path-validation.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,18 @@ export function isPathWithinAllowedDirectories(absolutePath: string, allowedDire
return false;
}

// Reject Windows Alternate Data Streams (ADS) to prevent path validation bypasses
if (process.platform === 'win32' || path.sep === '\\') {
const firstColonIndex = normalizedPath.indexOf(':');
if (firstColonIndex !== -1) {
const hasMoreThanOneColon = normalizedPath.indexOf(':', firstColonIndex + 1) !== -1;
const isValidDriveColon = firstColonIndex === 1 && /^[A-Za-z]$/.test(normalizedPath[0]);
if (hasMoreThanOneColon || !isValidDriveColon) {
return false;
}
}
}

// Verify it's absolute after normalization
if (!path.isAbsolute(normalizedPath)) {
throw new Error('Path must be absolute after normalization');
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