CVE-2022-21891
📋 TL;DR
CVE-2022-21891 is a spoofing vulnerability in Microsoft Dynamics 365 (on-premises) that allows an attacker to trick users into interacting with malicious content disguised as legitimate. This affects organizations running vulnerable on-premises Dynamics 365 deployments. Attackers could exploit this to perform phishing attacks or redirect users to malicious sites.
💻 Affected Systems
- Microsoft Dynamics 365 (on-premises)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An attacker could redirect users to malicious websites, steal credentials via phishing, or perform session hijacking by spoofing legitimate Dynamics 365 interfaces.
Likely Case
Phishing attacks where users are tricked into entering credentials on spoofed login pages or redirected to malicious sites.
If Mitigated
Limited impact with proper user awareness training, network segmentation, and monitoring for suspicious redirects.
🎯 Exploit Status
Exploitation requires user interaction (e.g., clicking a link) and some level of access to trick users.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply the security update from Microsoft's January 2022 Patch Tuesday or later
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2022-21891
Restart Required: Yes
Instructions:
1. Download the security update from Microsoft Update Catalog. 2. Apply the update to all affected Dynamics 365 on-premises servers. 3. Restart servers as required. 4. Test functionality post-patch.
🔧 Temporary Workarounds
Network Segmentation
allRestrict access to Dynamics 365 servers to trusted networks only
User Awareness Training
allEducate users about phishing risks and verifying URLs
🧯 If You Can't Patch
- Implement strict network access controls to limit exposure
- Monitor for suspicious redirects or unusual authentication patterns
🔍 How to Verify
Check if Vulnerable:
Check if Dynamics 365 on-premises version is unpatched for January 2022 updatesCheck Version:
Check Dynamics 365 version through administrative interfaces or server documentationVerify Fix Applied:
Verify the security update is installed via Windows Update history or server patch management tools📡 Detection & Monitoring
Log Indicators:
- Unusual redirect patterns in web server logs
- Failed authentication attempts from spoofed pages
Network Indicators:
- Unexpected external redirects from Dynamics 365 servers
SIEM Query:
search for web logs with status 302/301 redirects to unfamiliar domains from Dynamics servers