No longer able to upload/download files from a Cryptomator vault (references issue #17966)

[Steffen72]

I'd like to re-open issue #17966 or a new one covering the following issues:

OS: Windows 11 25H2 x64 (latest patches)

Settings in Mountain Duck: See screenshot

I've been experiencing the same behavior as in #17966 with Mountain Duck on my local Cryptomator vault:

• Open and unlock Cryptomator vault in Mountain Duck
• I can see all files in the vault with their correct names, same with directories
• Windows Explorer complains about missing permissions when reading (opening or copying) a file from the vault
• Windows Explorer complains about missing permissions when writing (e.g. copying) a file to the vault

I have not tried to delete something for hopefully obvious reasons.

• The Cryptomator vault itself behaves just fine with latest Cryptomator app
• I can also create a new vault with Cryptomator, and after releasing it there and opening it with Mountain Duck it immediately shows the same issues as described before

I have this issue with both my existing Cryptomator vault and also one created from scratch (using latest Cryptomator). No difference.

It all started with Mountain Duck version 5.2.1 release, and it's still persistent with the latest 5.3.0 release. The last version which has worked for me without issues was 5.2.0.

I assume something has been broken between 5.2.0 and 5.2.1 which I had hoped to be fixed in 5.3.0, but it hasn't (so far).

Stack Trace information:

2026-06-22 13:49:21,820 [directory-indexer-3] INFO  audit.cache - setattr Path{path='/D:/Cryptomator/Test/WILLKOMMEN.rtf', type=[file, decrypted]}, attributes=PathAttributes{accessed=1782127800548, size=573, modified=1782127785166, created=1782127785156, owner='null', group='null', permission=ch.cyberduck.core.StaticPermission@192122bb, acl={}, checksum='null', etag='null', storageClass='null', encryption='none', versionId='null', fileId='null', lockId='null', duplicate=false, hidden=false, trashed=false, revision=null, region='null', metadata={}', custom={}', verdict=null'}, prune=true
2026-06-22 13:49:21,821 [directory-indexer-3] INFO  audit.cache - setattr Path{path='/D:/Cryptomator/Test', type=[directory, vault]}, attributes=PathAttributes{accessed=-1, size=-1, modified=-1, created=-1, owner='null', group='null', permission=--, acl={}, checksum='null', etag='null', storageClass='null', encryption='none', versionId='null', fileId='null', lockId='null', duplicate=null, hidden=null, trashed=null, revision=null, region='null', metadata={}', custom={}', verdict=null'}, prune=false
2026-06-22 13:50:18,545 [Thread-143] INFO  audit.cloudfiles - fetchdata Path{path='/D:/Cryptomator/Test/WILLKOMMEN.rtf', type=[file, decrypted]} requiredfileoffset=0, requiredlength=573, optionalfileoffset=0, optionallength=0, process=C:\WINDOWS\Explorer.EXE with id 17120
2026-06-22 13:50:18,575 [Thread-143] WARN  audit.fs - Map failure BackgroundException{class=class ch.cyberduck.core.exception.AccessDeniedException, file=Path{path='/D:/Cryptomator/Test/d/YK/R4EAELQXTASCSTY3IFGKQ5KYU4XC4P/Q3yZa7Wo3eam8XljoAYdF1Q4on1-eyPCNXwje3Ez.c9r', type=[file, encrypted]}, message='Zugriff verweigert', detail='Download von Q3yZa7Wo3eam8XljoAYdF1Q4on1-eyPCNXwje3Ez.c9r fehlgeschlagen', cause='null'}
2026-06-22 13:50:18,575 [Thread-143] ERROR Ch.Iterate.Mountainduck.Cloudfiles.CloudFilesExceptionHandler - Mapped exception in "FetchData" to status 0xc000cf18
BackgroundException{class=class ch.cyberduck.core.exception.AccessDeniedException, file=Path{path='/D:/Cryptomator/Test/d/YK/R4EAELQXTASCSTY3IFGKQ5KYU4XC4P/Q3yZa7Wo3eam8XljoAYdF1Q4on1-eyPCNXwje3Ez.c9r', type=[file, encrypted]}, message='Zugriff verweigert', detail='Download von Q3yZa7Wo3eam8XljoAYdF1Q4on1-eyPCNXwje3Ez.c9r fehlgeschlagen', cause='null'}
	at ch.cyberduck.core.features.Read.preflight(Read.java:56)
	at ch.cyberduck.core.cryptomator.features.CryptoReadFeature.preflight(CryptoReadFeature.java:95)
	at ch.cyberduck.core.vault.registry.VaultRegistryReadFeature.preflight(VaultRegistryReadFeature.java:52)
	at ch.iterate.mountainduck.fs.FilesystemPreflight$ReadC
<img width="343" height="236" alt="Screenshot" src="https://github.com/user-attachments/assets/031be072-c6e2-4f08-92fb-871afff8bc96" />
apability.preflight(FilesystemPreflight.java:82)
	at ch.iterate.mountainduck.fs.FilesystemPreflight.preflight(FilesystemPreflight.java:32)
	at ch.iterate.mountainduck.fs.FailFastFilesystemOperations.open(FailFastFilesystemOperations.java:68)
	at cli.Ch.Iterate.Mountainduck.Cloudfiles.CloudFilesFilesystem.FetchData(Unknown Source)
	at cli.Ch.Iterate.Mountainduck.Cloudfiles.CloudFilesFilesystem.CfWrapper.ICloudFilesHandler.FetchData(Unknown Source)
	at cli.ABI.CfWrapper.ICloudFilesHandler.Do_Abi_FetchData_5(Unknown Source)
2026-06-22 13:50:26,597 [directory-indexer-1] INFO  audit.cache - setattr Path{path='/D:/Cryptomator/Test/WILLKOMMEN.rtf', type=[file, decrypted]}, attributes=PathAttributes{accessed=1782127800548, size=573, modified=1782127785166, created=1782127785156, owner='null', group='null', permission=ch.cyberduck.core.StaticPermission@192122bb, acl={}, checksum='null', etag='null', storageClass='null', encryption='none', versionId='null', fileId='null', lockId='null', duplicate=false, hidden=false, trashed=false, revision=null, region='null', metadata={}', custom={}', verdict=null'}, prune=true
2026-06-22 13:50:26,598 [directory-indexer-1] INFO  audit.cache - setattr Path{path='/D:/Cryptomator/Test', type=[directory, vault]}, attributes=PathAttributes{accessed=-1, size=-1, modified=-1, created=-1, owner='null', group='null', permission=--, acl={}, checksum='null', etag='null', storageClass='null', encryption='none', versionId='null', fileId='null', lockId='null', duplicate=null, hidden=null, trashed=null, revision=null, region='null', metadata={}', custom={}', verdict=null'}, prune=false

[Steffen72]

Hi @dkocher,

is there any chance to get some short-term feedback, please? This bug is really annoying, and I can't believe that I'm the only one experiencing this. I bought Mountain Duck specifically for this functionality, since Cryptomator's own app has been prone to crashes.

However, losing information or not being able to access it anymore is killing my primary use case.

[Steffen72]

This issue is still persistent with Mountain Duck 5.3.1, released today.

@dkocher: I feel pretty much left alone with this issue, as I do not get any response -- neither on the referenced bug, nor on this discussion.

10 days now, and counting. Not a single word on it.

[dkocher]

Sorry for the radio silence, missed this thread.

[Steffen72]

No worries. And thanks for the update.

[dkocher]

I will see that we can provide a fix for the next bugfix update and keep this thread updated.