In the world of computer security, the discovery of new vulnerabilities can serve as a wake-up call for software developers and IT professionals alike. CVE-2023-21690, explicitly referring to a critical flaw in Microsoft's Protected Extensible Authentication Protocol (PEAP), is no exception. This vulnerability allows attackers to potentially gain control of affected systems remotely, execute malicious code, and potentially compromise sensitive data.

In this post, we'll dive deep into CVE-2023-21690, unraveling the details of the exploit, as well as analyze an example of how it could be leveraged by malicious actors. We'll also take a look at the original sources and reference materials, providing you with a comprehensive understanding of this critical vulnerability. But first, let's start with a brief overview of what Microsoft's PEAP is all about.

What is Microsoft's Protected Extensible Authentication Protocol (PEAP)?

PEAP is a widely-used authentication method that provides a secure, encrypted method to transmit data and authentication credentials over a wireless or wired network. It's often used for networks that rely on WPA2-Enterprise or WPA3-Enterprise security protocols or in organizations that require an added layer of security for their network access points.

The flaw - CVE-2023-21690

CVE-2023-21690 is a remote code execution (RCE) vulnerability affecting Microsoft's PEAP implementation. The vulnerability exists due to improper handling and validation of authentication credentials and encrypted data, specifically within the handshake process. The flaw allows unauthenticated, remote attackers to execute arbitrary code on vulnerable systems potentially.

The exploit - How CVE-2023-21690 works

The exploitation of CVE-2023-21690 typically involves intercepting network traffic and injecting a carefully crafted payload. Below is a simplified code snippet demonstrating an attacker's possible approach to exploiting this vulnerability:

import socket
import peap_payload_generator

target_ip = ""
target_port = 1812

# Generate malicious PEAP payload
peap_payload = peap_payload_generator.generate_malicious_payload()

# Create a UDP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# Send the malicious payload to the target
sock.sendto(peap_payload, (target_ip, target_port))

This code snippet demonstrates the most basic approach to exploiting the vulnerability. For your convenience, we highly encourage you to explore the original sources and references for a more comprehensive understanding and depth.

1. CVE-2023-21690 Original advisory
2. Microsoft Security Advisory
3. NVD - National Vulnerability Database

Mitigation and countermeasures

Microsoft has already acknowledged the existence of CVE-2023-21690 and provided patches for the affected systems via the Microsoft Security Advisory linked above. Network administrators and IT professionals are highly encouraged to apply the provided patches promptly to reduce the risk of exploitation. Additionally, administrators should consider implementing best practices for network access control and enforcing strict access policies for devices connecting to their networks.


CVE-2023-21690 is a dangerous vulnerability in Microsoft's PEAP, and understanding its potential impact is crucial for securing networks and systems from potential attackers. Familiarizing yourself with this vulnerability and the associated exploit, along with the code snippet, is critical for anticipating potential threats and staying safe in an ever-evolving landscape of cybersecurity.

In the future, keep an eye out for more posts like this one, where we explore high-profile vulnerabilities, threats, and exploits to help you stay informed and, more importantly, secure. Stay safe out there!


Published on: 02/14/2023 20:15:00 UTC
Last modified on: 02/24/2023 14:04:00 UTC