CVE-2020-7036
📋 TL;DR
This XML External Entity (XXE) vulnerability in Avaya Callback Assist allows authenticated remote attackers to read files on the affected system by processing malicious XML input. It affects all versions of Callback Assist 4.0.x before 4.7.1.1 Patch 7. Organizations using vulnerable versions of this contact center software are at risk.
💻 Affected Systems
- Avaya Callback Assist
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through sensitive file disclosure including configuration files, credentials, or system files leading to further attacks.
Likely Case
Unauthorized reading of arbitrary files on the server, potentially exposing sensitive configuration data or customer information.
If Mitigated
Limited impact with proper network segmentation and file system permissions restricting accessible files.
🎯 Exploit Status
XXE vulnerabilities are well-understood attack vectors with established exploitation patterns. Authentication requirement adds a barrier but doesn't prevent exploitation by authorized malicious users.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.7.1.1 Patch 7
Vendor Advisory: https://downloads.avaya.com/css/P8/documents/101075450
Restart Required: Yes
Instructions:
1. Download patch from Avaya support portal. 2. Backup current configuration. 3. Apply patch following Avaya installation guide. 4. Restart Callback Assist services. 5. Verify successful installation.
🔧 Temporary Workarounds
Disable XML External Entity Processing
allConfigure XML parser to disable external entity resolution
Configuration depends on specific XML parser implementation. For Java-based parsers: set features like XMLConstants.FEATURE_SECURE_PROCESSING to true.
Input Validation and Filtering
allImplement strict input validation to reject XML containing external entity declarations
Implement XML schema validation or regex filtering for DOCTYPE declarations in incoming XML data.
🧯 If You Can't Patch
- Implement network segmentation to isolate Callback Assist from sensitive systems
- Apply strict file system permissions to limit accessible files
🔍 How to Verify
Check if Vulnerable:
Check Callback Assist version via admin interface or configuration files. If version is 4.0.x and lower than 4.7.1.1 Patch 7, system is vulnerable.Check Version:
Check version in Callback Assist web interface under Administration > System Information or examine configuration files.Verify Fix Applied:
Verify version shows 4.7.1.1 Patch 7 or higher in admin interface. Test XML processing with test payloads containing external entities.📡 Detection & Monitoring
Log Indicators:
- Unusual XML parsing errors
- File access attempts from XML parser context
- Large XML payloads containing DOCTYPE declarations
Network Indicators:
- XML requests containing external entity references
- Outbound connections from Callback Assist to unexpected internal systems
SIEM Query:
source="callback-assist-logs" AND (message="*DOCTYPE*" OR message="*ENTITY*" OR message="*XXE*")