[Bug]: Windows Client fails to sync new folders after Windows Update KB5065789 - ACL "insufficient memory" error #8860
Description
⚠️ Before submitting, please verify the following: ⚠️
- This is a bug, not a question or a configuration issue.
- This issue is not already reported on Github (I've searched it).
- Nextcloud Server and Desktop Client are up to date. See Server Maintenance and Release Schedule and Desktop Releases for supported versions.
- I agree to follow Nextcloud's Code of Conduct
Bug description
The Nextcloud Windows client fails to synchronize newly created folders from an SMB share mounted as external storage. The client logs show an "insufficient memory error" when calling InitializeAcl, causing the client to incorrectly treat folders as read-only.
Environment:
Nextcloud Client: 3.17.2 (build 20250916)
OS: Windows 11 with KB5065789 installed
Setup: SMB share mounted as read-only external storage in Nextcloud
Other clients: Android, macOS, Web interface - all working correctly
Timing: The issue was noticed on October 9, 2025. Two recent changes occurred:
Nextcloud Client update to 3.17.2 (September 16, 2025)
Windows Update KB5065789 (September 30, 2025)
It's uncertain which change triggered the issue, or if it's a combination of both. The last successful folder creation date is unknown.
Steps to reproduce
Note: Exact reproduction steps are unclear due to uncertain timing.
Either: Update to Nextcloud Client 3.17.2 and/or install Windows Update KB5065789
Have an SMB share configured as external storage in Nextcloud (read-only mount for security)
Create a new folder on the SMB share via network drive or file manager
Observe that existing files in old folders sync normally
New folders fail to sync with error notification every 30 seconds
Client delays sync by 60 seconds due to "too many synchronization errors"
Expected behavior
New folders should sync successfully from SMB shares
The client should handle ACL permissions gracefully after Windows Updates or client updates
If ACL initialization fails, the client should use a fallback method or provide clear error messages
The sync should not fail with "insufficient memory" errors on standard folder operations
Which files are affected by this bug
Affected: All newly created folders on the SMB share (after the Windows Update)
Operating system
Windows
Which version of the operating system you are running.
Windows 11
Package
Official Windows MSI
Nextcloud Server version
31.0.8
Nextcloud Desktop Client version
3.17.2
Is this bug present after an update or on a fresh install?
Updated to a major version (ex. 3.16.3 to 3.17.0)
Are you using the Nextcloud Server Encryption module?
Encryption is Disabled
Are you using an external user-backend?
- Default internal user-backend
- LDAP/ Active Directory
- SSO - SAML
- Other
Nextcloud Server logs
[ info nextcloud.sync.filesystem ]: detected access denied ACL: assuming read-only folder: "C:\\Users\\user\\NextcloudSync\\Customers"
[ warning nextcloud.sync.filesystem ]: insufficient memory error when calling InitializeAcl "\\\\?\\C:\\Users\\user\\NextcloudSync\\Customers"
[ warning nextcloud.sync.propagator ]: Could not complete propagation of "Customers/New Folder" by OCC::PropagateLocalMkdir with status OCC::SyncFileItem::NormalErrorAdditional info
Workaround:
Running as Administrator: icacls "C:\Users\user\NextcloudSync\Customers" /reset /t immediately resolves the issue by resetting ACL permissions to Windows defaults.
Server-side encryption: No (E2EE disabled according to client logs showing e2ee: false)
The issue affects only the Windows client, suggesting a Windows-specific ACL handling problem
Client was updated through normal update cycle (exact previous version unknown, likely from 3.16.x to 3.17.2)