If you've been seeing backup failures since April 14 and can't figure out why, this is probably it.
What happened
On April 14, 2026, Microsoft shipped KB5083769 as part of Patch Tuesday – a cumulative security update for Windows 11 Pro. The update added certain kernel drivers to Microsoft's vulnerable driver blocklist. This broke backup applications that rely on those drivers to create VSS (Volume Shadow Copy Service) snapshots.
Microsoft has confirmed that the blocklisting was intentional and considers it a security improvement, not a bug. Which is cold comfort when your backups are failing.
What it looks like
- Backup plans fail with Error 2426: VSS timeout exceeded – meaning VSS couldn't complete a snapshot within the 2-hour window
- Running
vssadmin list writersin an elevated Command Prompt just sits there with "Waiting for responses" and never returns - System counters (Available Bytes, Committed Bytes, etc.) stop working
- Log collection may hang when trying to read those counters
What actually works right now
Option 1: Install update KB5083631 without uninstalling KB5083769 first, then reboot. This has resolved the issue for a number of users.
Option 2: Uninstall KB5083769 entirely, then reboot.
No official out-of-band fix from Microsoft yet.
If you're running MSP360 backups, the full diagnostic guide with step-by-step instructions is here: https://kb.msp360.com/backup/errors/2426-vss-timeout-exceeded
Happy to answer questions if anyone's running into edge cases.