Criticalic Security Flaw: Unmounted volume automatally remounts without credentials upon launching UTM Virtual Machine on macOS 26.5.1+ (Apple Silicon)

[Christian-SC26]

Expected behavior

The encrypted VeraCrypt volume should remain securely locked, isolated, and completely unmounted after explicitly executing the dismount command. Any third-party application (like UTM) attempting to access files previously stored on that volume should fail, throwing an error that the paths or virtual machine images are completely inaccessible.

Observed behavior

A severe isolation failure occurs. After the volume is successfully unmounted via the VeraCrypt GUI and disappears from both the slot list and the Finder sidebar, it leaves "ghost" file descriptors behind in the macOS kernel.

When the UTM application is launched, it requests access to its recent VM paths. macOS recognizes the cached encryption keys still lingering in the system memory and instantly revives/remounts the active crypto-session. The VeraCrypt volume completely reappears as a mounted drive (/dev/disk4 / disk5) with full read/write privileges, bypassing all cryptographic checks, passwords, PIM, or keyfiles. Anyone with local access to the machine can manipulate, copy, or execute these files without restrictions.

Steps to reproduce

1. Mount a VeraCrypt volume (Standard or Hidden) containing UTM virtual machine images (.utm).
2. Run a virtual machine inside the UTM application located on this encrypted partition.
3. Shut down the virtual machine completely and close the UTM application.
4. Click "Dismount" inside the VeraCrypt GUI. Ensure the volume disappears from the active slots and the Finder sidebar.
5. Launch the UTM application again.
6. Run diskutil list in the Terminal or check the Finder sidebar; the previously unmounted volume is completely back online and accessible without any password prompts.

Screenshots

1. State 1: VeraCrypt open, volume unmounted, UTM closed.

diskutil list shows only local storage (disk0 and disk3). No encrypted volumes are present in the system.
Refer to file: CleanShot 2026-06-16 at 18.39.25.jpg

2. State 2: Launching UTM without mounting anything in VeraCrypt.

Immediately after launching UTM, diskutil list reveals that the system automatically brought back the encrypted container as a ghost disk image without credentials:
Refer to file: CleanShot 2026-06-16 at 18.40.06.jpg

/dev/disk4 (disk image):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        +47.2 GB    disk4
/dev/disk5 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +47.2 GB    disk5
                                 Physical Store disk4
   1:                APFS Volume untitled                16.7 GB    disk5s1

Your Environment

VeraCrypt version: 1.26.29

Operating system and version: macOS 26.5.1

System type: MacBook Pro M3 Pro