CVE-2021-43764
📋 TL;DR
This stored Cross-Site Scripting (XSS) vulnerability in Adobe Experience Manager allows attackers to inject malicious JavaScript into vulnerable form fields. When users visit pages containing these compromised fields, their browsers execute the attacker's scripts. This affects AEM Cloud Service and AEM 6.5.10.0 and earlier versions.
💻 Affected Systems
- Adobe Experience Manager (AEM)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal user session cookies, perform actions as authenticated users, redirect to malicious sites, or install malware on victim systems.
Likely Case
Session hijacking, credential theft, defacement of web pages, or data exfiltration from user browsers.
If Mitigated
Limited impact with proper input validation, output encoding, and Content Security Policy (CSP) headers in place.
🎯 Exploit Status
Exploitation requires access to vulnerable form fields; typically requires some level of user interaction or content authoring access
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: AEM 6.5.11.0 or later
Vendor Advisory: https://helpx.adobe.com/security/products/experience-manager/apsb21-103.html
Restart Required: Yes
Instructions:
1. Download AEM 6.5.11.0 or later from Adobe distribution portal. 2. Apply the service pack following Adobe's installation guide. 3. Restart AEM instance. 4. For AEM Cloud Service, Adobe automatically applies patches.
🔧 Temporary Workarounds
Input Validation and Output Encoding
allImplement server-side input validation and proper output encoding for all user-controllable fields
Content Security Policy
allImplement strict Content Security Policy headers to restrict script execution
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) rules to block XSS payloads
- Restrict access to content authoring interfaces to trusted users only
🔍 How to Verify
Check if Vulnerable:
Check AEM version via AEM Web Console (/system/console) or by examining CRX package managerCheck Version:
curl -u admin:password http://localhost:4502/system/console/status-productinfoVerify Fix Applied:
Verify AEM version is 6.5.11.0 or later and test form fields for XSS payload acceptance📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to form endpoints with script tags
- Multiple failed login attempts followed by form submissions
Network Indicators:
- HTTP requests containing script tags or JavaScript payloads in form data
SIEM Query:
source="aem_access.log" AND ("<script>" OR "javascript:" OR "onerror=" OR "onload=")