Malware exploits decade old Windows bug, which has an opt-in fix

Martin Brinkmann
Apr 3, 2023
Security, Windows
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9

A decade old Windows bug, for which a fix is available, is used by malware currently in attacks against Windows devices. Malware actors may exploit the vulnerability to add malicious code to signed Windows files without them losing their signed status.

Digital signatures are used on Windows to determine the authenticity of files. Most security solutions check for signatures when they check files on Windows machines.

What makes this exploit even more problematic is the fact that a fix is available, but that it is opt-in. If that was not enough, it appears that upgrades to Windows 11 may drop the fix, if applied in the Windows Registry.

Bleeping Computer reported this week that the VOIP communications company 3CX was compromised. The attackers managed to include malware into the company's desktop application for Windows. Two DLL files used by the desktop application were modified by the threat actors to include malware, more precisely, an information-stealing trojan.

What makes the attack special is that the attackers are exploiting CVE-2013-3900, WinVerifyTrust Signature Validation Vulnerability, which Microsoft confirmed in 2013 for the first time and has updated in early 2022 with additional information.

How to protect Windows devices against the attacks

windows cert padding check

Microsoft published an opt-in fix to address the issue in 2013, and it has been valid ever since.

Windows 64-bit versions may be protected with the following Registry code:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\Software\Microsoft\Cryptography\Wintrust\Config]
"EnableCertPaddingCheck"="1"

[HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Cryptography\Wintrust\Config]
"EnableCertPaddingCheck"="1"

Note: you need to paste the code into a plain text file and rename its file extension, so that it is .reg. We have uploaded a Zip archive with Registry files for 32-bit and 64-bit versions of Windows: windows-registry-fix

All you need to do is double-click on the file to add the information to the Registry (a verification prompt is displayed, which you need to allow).

A restart of the system is required. Delete the listed Registry values to undo the change at any time.

Enabling the changes will make non-confirming binaries "appear unsigned" and be rendered untrusted as a consequence.

Why opt-in?

Why did Microsoft release the patch this way, and did not integrate it directly into Windows? The extensive FAQ on the support page provides an answer. According to Microsoft, enabling the stricter verification behavior may "impact some installers" and also certain AppLocker behavior and Software Restriction Policies.

Closing Words

Windows administrators may check the listed Registry values above to verify if the devices are protected against the vulnerability. Windows devices that were upgraded to Windows 11 need to be rechecked, as the Registry values are likely no longer there after the upgrade. Note that applying the changes using policies should keep them enabled after the upgrade.

Summary
Malware exploits decade old Windows bug, which has an opt-in fix
Article Name
Malware exploits decade old Windows bug, which has an opt-in fix
Description
A decade old Windows bug, for which a fix is available, is used by malware currently in attacks against Windows devices.
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Ghacks Technology News
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Comments

  1. Dan Donx said on January 15, 2023 at 10:29 am
    Reply

    What mental age of reader are you targeting with the first sentence? 10?

    Why not write an article on how to *avoid* upgrading from W10 to W11. Analogous to those like me who avoided upgrading from 7 to 10 for as long as possible.

    If your paymaster Microsoft permits it, of course.

  2. Dexter said on January 15, 2023 at 11:14 am
    Reply

    5. Rufus
    6. Ventoy

    PS. I hate reading these “SEO optimized” articles.

    1. cdr said on January 15, 2023 at 3:32 pm
      Reply

      I used Rufus to create an installer for a 6th gen intel i5 that had MBR. It upgraded using Setup. No issues except for Win 11 always prompting me to replace my local account. Still using Win 10 Pro on all my other PCs to avoid the bullying.

  3. sv said on January 15, 2023 at 6:40 pm
    Reply

    bit pointless to upgrade for the sake of upgrading as you never know when you’ll get locked out because ms might suddenly not provide updates to unsupported systems.

    ps…. time travelling?
    written. Jan 15, 2023
    Updated • Jan 13, 2023

    1. Martin Brinkmann said on January 16, 2023 at 5:49 am
      Reply

      This happens when you schedule a post in WordPress and update it before setting the publication date.

  4. Anonymous said on January 16, 2023 at 8:24 am
    Reply

    Anyone willing to downgrade to this awful OS must like inflicting themselves with harm.

  5. basingstoke said on January 16, 2023 at 11:18 am
    Reply

    I have become convinced now that anybody who has no qualms with using Windows 11/10 must fit into one of the following brackets:

    1) Too young to remember a time before W10 and W11 (doesn’t know better)

    2) Wants to play the latest games on their PC above anything else (or deeply needs some software which already dropped W7 support)

    3) Doesn’t know too much about how computers work, worried that they’d be absolutely lost and in trouble without the “”latest security””

    4) Microsoft apologist that tries to justify that the latest “features” and “changes” are actually a good thing, that improve Windows

    5) Uses their computer to do a bare minimum of like 3 different things, browse web, check emails, etc, so really doesn’t fuss

    Obviously that doesn’t cover everyone, there’s also the category that:

    6) Actually liked W7 more than 10, and held out as long as possible before switching, begrudgingly uses 10 now

    Have I missed any group off this list?

    1. Heinz Strunk said on September 19, 2023 at 3:57 pm
      Reply

      You have missed in this group just about any professional user that uses business software like CAD programs or ERP Programs which are 99% of all professional users from this list.

      Linux doesn’t help anyone who is not a linux kid and apple is just a fancy facebook machine.

  6. ilev said on August 24, 2023 at 7:34 pm
    Reply

    Microsoft has removed KB5029351 update

    1. EP said on August 24, 2023 at 9:21 pm
      Reply

      only from windows update though
      KB5029351 is still available from the ms update catalog site

  7. Anonymous said on August 24, 2023 at 11:05 pm
    Reply

    1. This update is labaled as PREVIEW if it causes issues to unintelligent people, then they shouldn’t have allowed Preview updates ot install.

    2. I have installed it in a 11 years old computer, and no problems at all.

    3. Making a big drama over a bluescreen for an updated labeled as preview is ridiculous.

    This is probably another BS internet drama where people ran programs and scripts that modified the registry until they broke Windows, just for removing stuff that they weren’t even using just for the sake of it.
    Maybe people should stop playing geeks and actually either use Windows 10 or Windows 11, but don’t try to modify things just for the sake of it.

    Sometimes removing or stopping things (like defender is a perfect example) only need intelligence, not scripts or 3rd party programs that might mess with windows.

  8. john said on August 24, 2023 at 11:17 pm
    Reply

    Windows 11 was a pointless release, it was just created because some of the Windows team wanted to boost sales with some sort of new and improved Windows 10. Instead, Microsoft cannot support one version well let alone two.

    1. John G. said on August 25, 2023 at 12:08 pm
      Reply

      Windows 11 is the worst ugly shame by Microsoft ever. They should release with every new W11 version a complete free version of Starallback inside just to make this sh** OS functionally again.

  9. EP said on August 25, 2023 at 3:10 pm
    Reply

    motherboard maker MSI has recently released a statement regarding the “unsupported processor” blue screen error for their boards using Intel 600/700 series chipsets & to avoid the KB5029351 Win11 update:
    https://www.msi.com/news/detail/MSI-On–UNSUPPORTED-PROCESSOR–Error-Message-of-Windows-11-Update-KB5029351-Preview-142215

  10. EP said on August 29, 2023 at 7:32 pm
    Reply

    check out the following recent articles:

    Neowin – Microsoft puts little blame on its Windows update after UNSUPPORTED PROCESSOR BSOD bug:
    https://www.neowin.net/news/microsoft-puts-little-blame-on-its-windows-update-after-unsupported-processor-bsod-bug/

    BleepingComputer – Microsoft blames ‘unsupported processor’ blue screens on OEM vendors:
    https://www.bleepingcomputer.com/news/microsoft/microsoft-blames-unsupported-processor-blue-screens-on-oem-vendors/

  11. Leonard Britvolli said on August 30, 2023 at 10:33 pm
    Reply

    While there may be changes or updates to the Windows 10 Store for Business and Education in the future, it is premature to conclude that it will be discontinued based solely on rumors.

  12. sembrador said on September 5, 2023 at 9:32 pm
    Reply

    My advice, I left win 15 years ago. Now I’m a happy linux user (linuxmint) but there is Centos, Fedora, Ubuntu depending on your needs.

  13. EP said on September 6, 2023 at 11:55 am
    Reply

    motherboard maker MSI has recently released new BIOS/firmware updates for their Intel 600 & 700 series motherboards to fix the “UNSUPPORTED_PROCESSOR” problem (Sept. 6):

    https://www.msi.com/news/detail/Updated-BIOS-fixes-Error-Message–UNSUPPORTED-PROCESSOR–caused-BSOD-on-MSI-s-Intel-700-and-600-Series-Motherboards-142277

  14. Raphael Benzo said on September 24, 2023 at 9:52 pm
    Reply

    I try to disable the Diagnostics Tracking Service (Connected Devices Platform User Services) but it wont let me disable it, any help will be greatly appreciated.
    Tank you for your help

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