In April 2022, Microsoft revealed a critical vulnerability in Windows: CVE-2022-26926. This security flaw lets attackers run malicious code just by sending a crafted file or email to the victim. The bug sits inside a very old Windows component called Windows Address Book (WAB). In this post, we break down how the vulnerability works, how it might be exploited, and what you must do to stay protected—using simple language for everyone to understand.

What is CVE-2022-26926?

CVE-2022-26926 is a remote code execution (RCE) vulnerability found in the Windows Address Book – the part of Windows that stores contact information for apps like Outlook Express and Windows Mail. An attacker who takes advantage of this bug could run code on your PC, potentially letting them install malware, steal sensitive info, or get deeper access to your files and your network.

Attack vector: Network (email attachment, trick website, SMB share, etc.)

- Original advisory: Microsoft Security Guide ADV2200022

How Does the Vulnerability Work?

The vulnerability comes from how Windows Address Book parses specially-crafted .WAB files. If bad data is read from a file, a memory error occurs. More specifically, the flaw is related to invalid pointer dereference or memory corruption. When Windows attempts to read the malicious file (for example, if a user opens it or a script loads it in the background), an attacker can plant code into memory and force Windows to run it.

How Attackers Can Use It

1. Send a Booby-Trapped .WAB File: The attacker crafts a malicious Windows Address Book file. They might send it as an email attachment or make it available on a website or a network share.
2. Convince the User to Open It: This could be social engineering (like pretending it’s a new contact list from HR).
3. Trigger the Exploit: When the victim opens or previews the file, the exploit runs, and the attacker gains control over the machine—potentially with the same privileges as the user.

Proof-of-Concept Exploit (Demo)

Here's a simplified breakdown of potential exploit steps.

[PoC] Python script to craft a malformed WAB file

This script creates a specially-mangled .wab file that crashes vulnerable Address Book apps – showing the flaw can be triggered. (This is NOT weaponized; real attack code would be more complex!)

# create_malicious_wab.py
# Generates a malformed Windows Address Book file

file_header = b'WAB4'  # WAB file signature
malicious_payload = b'\x41' * 1024  # Overflow buffer with A's

with open('exploit.wab', 'wb') as f:
    f.write(file_header)
    f.write(malicious_payload)

print("Malicious WAB file created as exploit.wab")

What happens?
If a vulnerable app loads exploit.wab, it may crash or (in a real attack) let the attacker execute code.

For detailed format information, check the old WAB SDK docs (archived).

Real-World Attack Scenarios

- Email Phishing: A bad guy sends what looks like a contact file from a colleague or business partner. Opening it is enough to get infected.
- Web Drive-by: Visiting a hacked webpage triggers an iFrame or JS to load a .wab file via the browser (older IE integration).
- Network Shares: Using SMB (e.g., from a networked printer or fake “backups” folder), an attacker plants the .wab file, convincing a user to “import new contacts."

How Was It Fixed?

Microsoft patched this vulnerability on May 10, 2022 as part of Patch Tuesday.

The patch fixes how Windows parses .wab files, stopping malicious input from causing code execution.

- Advisory and updates can be found here: Microsoft Security Update Guide: CVE-2022-26926

Update Windows. Install all updates from May 2022 or later.

- Don’t open suspicious email attachments! Even files from people you know can be dangerous if their accounts are hacked.

Further Reading

- Microsoft's Official Advisory
- NIST NVD summary
- BleepingComputer write-up (covers related vulnerabilities)

Final Thoughts

Windows Address Book is a relic, but leftover code can still punch big holes in modern Windows systems. CVE-2022-26926 is a classic story: an old feature turning into a new security nightmare. If you haven't yet, patch up and be wary of strange files—contacts can be just as dangerous as Office docs or EXEs.

Stay safe! If you work in IT or security, consider removing WAB support on enterprise devices and educate your users about the risks of unknown contacts.


*If you found this useful, share with your team or IT friends—spread awareness, not exploits!* 🚨

Timeline

Published on: 05/10/2022 21:15:00 UTC
Last modified on: 05/19/2022 21:13:00 UTC