peass-ng/PEASS-ng · error · ArgumentException

Resources.Not_A_Valid_Guid

Error message

Resources.Not_A_Valid_Guid

What it means

EnumerateVolumeMountPoints throws ArgumentException with message Resources.Not_A_Valid_Guid when volumeGuid is non-empty but does not start with the volume prefix "\\?\Volume{" (case-insensitive). The method only accepts a volume GUID path, not a drive letter or arbitrary path.

Source

Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/AlphaFS/Device/Volume/Volume.EnumerateVolumeMountPoints.cs:45

using winPEAS._3rdParty.AlphaFS;

namespace Alphaleonis.Win32.Filesystem
{
   public static partial class Volume
   {
      /// <summary>[AlphaFS] Returns an enumerable collection of <see cref="String"/> of all mounted folders (volume mount points) on the specified volume. </summary>
      /// <exception cref="ArgumentNullException"/>
      /// <exception cref="ArgumentException"/>
      /// <param name="volumeGuid">A <see cref="string"/> containing the volume <see cref="Guid"/>.</param>
      /// <returns>An enumerable collection of <see cref="String"/> of all volume mount points on the specified volume.</returns>
      [SecurityCritical]
      public static IEnumerable<string> EnumerateVolumeMountPoints(string volumeGuid)
      {
         if (Utils.IsNullOrWhiteSpace(volumeGuid))
            throw new ArgumentNullException("volumeGuid");

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


         // A trailing backslash is required.
         volumeGuid = Path.AddTrailingDirectorySeparator(volumeGuid, false);


         var buffer = new StringBuilder(NativeMethods.MaxPathUnicode);


         using (new NativeMethods.ChangeErrorMode(NativeMethods.ErrorMode.FailCriticalErrors))
         using (var handle = NativeMethods.FindFirstVolumeMountPoint(volumeGuid, buffer, (uint)buffer.Capacity))
         {
            var lastError = Marshal.GetLastWin32Error();

            if (!NativeMethods.IsValidHandle(handle, false))
            {
               switch ((uint)lastError)
               {

View on GitHub (pinned to 53fb989abc)

Solutions

1. Convert the input to a volume GUID path first via Volume.GetVolumeGuid(path)
2. Ensure the string matches \\?\Volume{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}\ format before calling
3. Catch ArgumentException and fall back to Volume.GetVolumeGuid to normalize the input

Example fix

// before
Volume.EnumerateVolumeMountPoints("C:\");
// after
var guid = Volume.GetVolumeGuid("C:\");
Volume.EnumerateVolumeMountPoints(guid); // \\?\Volume{...}\

if (!volumeGuid.StartsWith(@"\\?\Volume{", StringComparison.OrdinalIgnoreCase))
    volumeGuid = Volume.GetVolumeGuid(volumeGuid); // normalize drive letter to GUID path

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

try { Volume.EnumerateVolumeMountPoints(guid); }
catch (ArgumentException ex) { Log.Error($"Not a valid volume GUID path: {ex.Message}"); }

When it happens

Trigger: Passing "C:\", a device path like "\\.\C:", a GUID without the \\?\Volume{ prefix, or a malformed GUID string to Volume.EnumerateVolumeMountPoints.

Common situations: Mixing up drive-letter paths with volume GUID paths; truncating a GUID path when storing it; constructing the GUID string manually with the wrong prefix casing/format.

Related errors

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

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/5bef70f6459b6b4a. Report an issue: GitHub.