CVE-2023-21691
📋 TL;DR
This vulnerability in Microsoft's Protected Extensible Authentication Protocol (PEAP) allows an attacker to disclose sensitive information from memory. It affects systems using PEAP for authentication, particularly Windows servers and clients configured with PEAP. Attackers could potentially access credentials or other sensitive data.
💻 Affected Systems
- Windows Server
- Windows Client
📦 What is this software?
Windows 10 1507 by Microsoft
Windows 10 1507 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 20h2 by Microsoft
Windows 10 20h2 by Microsoft
Windows 10 20h2 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 11 21h2 by Microsoft
Windows 11 21h2 by Microsoft
Windows 11 22h2 by Microsoft
Windows 11 22h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
An attacker could extract authentication credentials or other sensitive information from memory, leading to credential theft and potential lateral movement within the network.
Likely Case
Information disclosure of memory contents that may include authentication-related data or system information.
If Mitigated
Limited impact with proper network segmentation and monitoring, though information disclosure still occurs.
🎯 Exploit Status
Requires network access and ability to intercept/modify PEAP authentication traffic. Attacker needs to be positioned on the network path.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft's monthly security updates for January 2023 or later
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21691
Restart Required: Yes
Instructions:
1. Apply the latest Windows security updates from Microsoft. 2. Restart affected systems. 3. Verify the patch is applied using Windows Update history or system information.
🔧 Temporary Workarounds
Disable PEAP authentication
windowsSwitch to alternative authentication methods that don't use PEAP
Configure network policies to use EAP-TLS or other non-PEAP methods
Network segmentation
allIsolate authentication traffic to prevent interception
Implement VLAN segmentation for authentication servers and clients
🧯 If You Can't Patch
- Implement strict network monitoring for unusual authentication patterns
- Use network encryption (IPsec) to protect authentication traffic
🔍 How to Verify
Check if Vulnerable:
Check if system uses PEAP for authentication in network policies and verify Windows version against affected versions listCheck Version:
wmic os get caption, version, buildnumberVerify Fix Applied:
Verify Windows Update history shows the January 2023 or later security updates are installed📡 Detection & Monitoring
Log Indicators:
- Unusual authentication failures
- Multiple authentication attempts from same source
- PEAP protocol errors in event logs
Network Indicators:
- Unusual traffic patterns during authentication
- PEAP protocol manipulation attempts
SIEM Query:
EventID=6272 OR EventID=6273 with PEAP authentication failures