peass-ng/PEASS-ng · error · ArgumentNullException

volumeGuid

Error message

volumeGuid

What it means

SetVolumeMountPoint throws ArgumentNullException ("volumeGuid") when the second argument is null/empty/whitespace, and ArgumentException (Resources.Not_A_Valid_Guid) when it is non-empty but lacks the "\\?\Volume{" prefix. The GUID argument must be a full volume GUID path of the form \\?\Volume{...}\.

Source

Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/AlphaFS/Device/Volume/Volume.SetVolumeMountPoint.cs:48

   public static partial class Volume
   {
      /// <summary>[AlphaFS] Associates a volume with a Drive letter or a directory on another volume.</summary>
      /// <exception cref="ArgumentException"/>
      /// <exception cref="ArgumentNullException"/>
      /// <param name="volumeMountPoint">
      ///   The user-mode path to be associated with the volume. This may be a Drive letter (for example, "X:\")
      ///   or a directory on another volume (for example, "Y:\MountX\").
      /// </param>
      /// <param name="volumeGuid">A <see cref="string"/> containing the volume <see cref="Guid"/>.</param>      
      [SuppressMessage("Microsoft.Design", "CA1062:Validate arguments of public methods", MessageId = "1", Justification = "Utils.IsNullOrWhiteSpace validates arguments.")]
      [SecurityCritical]
      public static void SetVolumeMountPoint(string volumeMountPoint, string volumeGuid)
      {
         if (Utils.IsNullOrWhiteSpace(volumeMountPoint))
            throw new ArgumentNullException("volumeMountPoint");

         if (Utils.IsNullOrWhiteSpace(volumeGuid))
            throw new ArgumentNullException("volumeGuid");

         if (!volumeGuid.StartsWith(Path.VolumePrefix + "{", StringComparison.OrdinalIgnoreCase))
            throw new ArgumentException(Resources.Not_A_Valid_Guid, "volumeGuid");


         volumeMountPoint = Path.GetFullPathCore(null, false, volumeMountPoint, GetFullPathOptions.AsLongPath | GetFullPathOptions.AddTrailingDirectorySeparator | GetFullPathOptions.FullCheck);


         // This string must be of the form "\\?\Volume{GUID}\"
         volumeGuid = Path.AddTrailingDirectorySeparator(volumeGuid, false);


         // ChangeErrorMode is for the Win32 SetThreadErrorMode() method, used to suppress possible pop-ups.
         using (new NativeMethods.ChangeErrorMode(NativeMethods.ErrorMode.FailCriticalErrors))
         {
            // SetVolumeMountPoint()
            // 2014-01-29: MSDN does not confirm LongPath usage but a Unicode version of this function exists.

View on GitHub (pinned to 53fb989abc)

Solutions

1. Resolve the GUID path via Volume.GetVolumeGuid("E:\") and pass that result
2. Validate the argument starts with "\\?\Volume{" before calling
3. Catch both ArgumentNullException and ArgumentException and surface a clear config error

Example fix

// before
Volume.SetVolumeMountPoint("C:\Mount", "E:\");
// after
string guid = Volume.GetVolumeGuid("E:\");
Volume.SetVolumeMountPoint("C:\Mount", guid); // \\?\Volume{...}\

if (string.IsNullOrWhiteSpace(volumeGuid) || !volumeGuid.StartsWith(@"\\?\Volume{", StringComparison.OrdinalIgnoreCase))
    volumeGuid = Volume.GetVolumeGuid(driveLetter); // resolve from a path if needed

static bool IsVolumeGuidPath(string s) => !string.IsNullOrWhiteSpace(s) && s.StartsWith(@"\\?\Volume{", StringComparison.OrdinalIgnoreCase);

try { Volume.SetVolumeMountPoint(mountDir, guid); }
catch (ArgumentException) { Log.Error($"volumeGuid must be \\\\?\\Volume{{...}}\\ format, got: {guid}"); }
catch (ArgumentNullException) { Log.Error("volumeGuid was null/empty"); }

When it happens

Trigger: Calling Volume.SetVolumeMountPoint(dir, null); passing a drive letter "E:\" or bare GUID string without the \\?\Volume{ prefix as volumeGuid.

Common situations: Hard-coding a volume GUID that was truncated or reformatted; storing GUIDs without the device prefix in config; passing a drive letter where a volume GUID path is required.

Related errors

• Resources.Not_A_Valid_Guid
• Resources.Not_A_Valid_Guid
• volumeGuid
• volumeGuid
• volumePathName

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/71704d94636df66d. Report an issue: GitHub.