CVE-2021-29140
📋 TL;DR
This CVE describes an XML External Entity (XXE) vulnerability in Aruba ClearPass Policy Manager that allows remote attackers to read arbitrary files on the system or conduct server-side request forgery attacks. Affected organizations are those running ClearPass Policy Manager versions prior to 6.9.5, 6.8.9, or 6.7.14-HF1. The vulnerability can be exploited without authentication in certain configurations.
💻 Affected Systems
- Aruba ClearPass Policy Manager
📦 What is this software?
Clearpass by Arubanetworks
Clearpass by Arubanetworks
⚠️ Risk & Real-World Impact
Worst Case
Remote attacker gains full system access, reads sensitive files (including passwords and configuration data), and potentially executes arbitrary code through SSRF or other chained attacks.
Likely Case
Attacker reads sensitive configuration files, obtains credentials, and uses them to pivot deeper into the network or compromise other systems.
If Mitigated
Limited information disclosure if network segmentation and proper XML parsing configurations are in place.
🎯 Exploit Status
XXE vulnerabilities are well-understood and often have public exploit code available, though no specific PoC for this CVE has been published. The vulnerability requires sending specially crafted XML to vulnerable endpoints.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.9.5, 6.8.9, or 6.7.14-HF1
Vendor Advisory: https://www.arubanetworks.com/assets/alert/ARUBA-PSA-2021-009.txt
Restart Required: Yes
Instructions:
1. Backup ClearPass configuration and data. 2. Download appropriate patch version from Aruba support portal. 3. Apply patch following Aruba's upgrade documentation. 4. Restart ClearPass services. 5. Verify successful upgrade and functionality.
🔧 Temporary Workarounds
Disable XML External Entity Processing
linuxConfigure XML parsers to disable external entity resolution
# Requires modifying application configuration files
# Set XML parser properties: FEATURE_SECURE_PROCESSING = true
# Disable DTD processing and external entity expansion
Network Segmentation
allRestrict network access to ClearPass management interfaces
# Example firewall rule (iptables):
iptables -A INPUT -p tcp --dport 443 -s trusted_networks -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Implement strict network access controls to limit which systems can communicate with ClearPass
- Deploy a web application firewall (WAF) with XXE protection rules enabled
🔍 How to Verify
Check if Vulnerable:
Check ClearPass version via web interface (Admin > Support > About) or CLI command 'show version'Check Version:
show versionVerify Fix Applied:
Verify version is 6.9.5, 6.8.9, or 6.7.14-HF1 or later. Test XML parsing with safe payloads.📡 Detection & Monitoring
Log Indicators:
- Unusual XML parsing errors in application logs
- Multiple failed authentication attempts followed by XML processing
- Large XML payloads in HTTP requests
Network Indicators:
- HTTP requests containing XML with external entity declarations
- Outbound connections from ClearPass to unexpected internal systems
SIEM Query:
source="clearpass" AND ("XXE" OR "DOCTYPE" OR "ENTITY" OR "SYSTEM")