CVE-2024-21395
📋 TL;DR
This vulnerability allows attackers to inject malicious scripts into Microsoft Dynamics 365 (on-premises) web pages, which are then executed in victims' browsers when they view those pages. It affects organizations running vulnerable versions of Microsoft Dynamics 365 on-premises deployments. Attackers could steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users.
💻 Affected Systems
- Microsoft Dynamics 365 (on-premises)
📦 What is this software?
Dynamics 365 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Attackers steal administrator credentials, gain full control of the Dynamics 365 instance, access sensitive business data, and pivot to other internal systems.
Likely Case
Attackers steal user session cookies to impersonate legitimate users, access sensitive customer data, or modify business records.
If Mitigated
With proper input validation and output encoding, the attack surface is reduced, but the vulnerability still exists until patched.
🎯 Exploit Status
Requires attacker to have some level of access to the application, but exploitation is straightforward once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update Guide for specific patch versions
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-21395
Restart Required: Yes
Instructions:
1. Download the security update from Microsoft Update Catalog. 2. Apply the update to all affected Dynamics 365 servers. 3. Restart the servers as required. 4. Test application functionality after patching.
🔧 Temporary Workarounds
Implement Content Security Policy (CSP)
allConfigure CSP headers to restrict script execution sources and reduce XSS impact
Enable Input Validation
windowsConfigure Dynamics 365 to validate and sanitize all user inputs
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) with XSS protection rules
- Restrict access to Dynamics 365 to trusted IP ranges only
🔍 How to Verify
Check if Vulnerable:
Check Dynamics 365 version against Microsoft's security advisory for affected versionsCheck Version:
Check Dynamics 365 version in application administration panel or server registryVerify Fix Applied:
Verify the patch version is installed and test for XSS vulnerabilities using security scanning tools📡 Detection & Monitoring
Log Indicators:
- Unusual script tags in HTTP requests
- Multiple failed input validation attempts
- Suspicious user agent strings
Network Indicators:
- Malicious script payloads in HTTP traffic
- Unexpected redirects from Dynamics 365 pages
SIEM Query:
source="dynamics365" AND (http_request contains "<script>" OR http_request contains "javascript:")