Security News > 2022 > October > Actively exploited Windows MoTW zero-day gets unofficial patch
A free unofficial patch has been released for an actively exploited zero-day that allows files signed with malformed signatures to bypass Mark-of-the-Web security warnings in Windows 10 and Windows 11.
What made these Magniber JavaScript files stand out was that even though they contained a Mark-of-a-Web, Windows did not display any security warnings when they were launched.
When a malicious file with one of these malformed signatures is opened, instead of being flagged by Microsoft SmartScreen and showing a security warning, Windows would automatically allow the program to run.
As this zero-day vulnerability is actively exploited in ransomware attacks, the 0patch micro-patching service decided to release an unofficial fix that can be used until Microsoft releases an official security update.
In a 0patch blog post, co-founder Mitja Kolsek explains that this bug is caused by Windows SmartScreen's inability to parse the malformed signature in a file.
"While our patch fixes the most obvious flaw, its utility depends on the application opening the file using function DoSafeOpenPromptForShellExe in shdocvw.dll and not some other mechanism," warns Kolsek.
News URL
Related news
- Week in review: Exploited Ivanti Connect Secure zero-day, Patch Tuesday forecast (source)
- Microsoft January 2025 Patch Tuesday fixes 8 zero-days, 159 flaws (source)
- Microsoft fixes actively exploited Windows Hyper-V zero-day flaws (source)
- Windows Patch Tuesday hits snag with Citrix software, workarounds published (source)
- 7-Zip fixes bug that bypasses Windows MoTW security warnings, patch now (source)
- Patch procrastination leaves 50,000 Fortinet firewalls vulnerable to zero-day (source)
- Don't want your Kubernetes Windows nodes hijacked? Patch this hole now (source)
- Microsoft February 2025 Patch Tuesday fixes 4 zero-days, 55 flaws (source)
- Patch Tuesday: Microsoft Patches Two Actively Exploited Zero-Day Flaws (source)