CVE-2021-42853
📋 TL;DR
This directory traversal vulnerability in SteelCentral AppInternals Dynamic Sampling Agent allows attackers to read or delete arbitrary files on the server by manipulating the '/api/appInternals/1.0/agent/diagnostic/logs' API endpoint. Organizations using vulnerable versions of the SteelCentral AppInternals DSA are affected.
💻 Affected Systems
- Riverbed SteelCentral AppInternals Dynamic Sampling Agent
📦 What is this software?
Steelcentral Appinternals Dynamic Sampling Agent by Riverbed
View all CVEs affecting Steelcentral Appinternals Dynamic Sampling Agent →
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via sensitive file disclosure (passwords, configuration files) or deletion of critical system files leading to service disruption.
Likely Case
Unauthorized access to application logs, configuration files, and potentially sensitive data stored on the server.
If Mitigated
Limited impact with proper network segmentation and access controls preventing external access to the vulnerable endpoint.
🎯 Exploit Status
The vulnerability requires no authentication and can be exploited with simple HTTP requests containing directory traversal sequences.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 12.14.0 and later
Vendor Advisory: https://aternity.force.com/customersuccess/s/article/Directory-Traversal-Delete-Read-at-AgentDiagnosticServlet-CVE-2021-42853
Restart Required: Yes
Instructions:
1. Download SteelCentral AppInternals DSA version 12.14.0 or later from Riverbed support portal. 2. Stop the DSA service. 3. Install the updated version. 4. Restart the DSA service.
🔧 Temporary Workarounds
Network Access Restriction
linuxBlock external access to the vulnerable API endpoint using firewall rules.
iptables -A INPUT -p tcp --dport <DSA_PORT> -m string --string "/api/appInternals/1.0/agent/diagnostic/logs" --algo bm -j DROP
Web Server Configuration
allConfigure the web server to deny access to the vulnerable endpoint.
<Location "/api/appInternals/1.0/agent/diagnostic/logs">
Order deny,allow
Deny from all
</Location>
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the DSA from untrusted networks.
- Deploy a web application firewall (WAF) with directory traversal protection rules.
🔍 How to Verify
Check if Vulnerable:
Check if the DSA version is below 12.14.0 and test if the '/api/appInternals/1.0/agent/diagnostic/logs' endpoint accepts directory traversal sequences like '../../etc/passwd'.Check Version:
Check the DSA administration interface or configuration files for version information.Verify Fix Applied:
Verify the DSA version is 12.14.0 or later and confirm directory traversal attempts to the vulnerable endpoint are rejected.📡 Detection & Monitoring
Log Indicators:
- HTTP requests containing '..' or directory traversal patterns to '/api/appInternals/1.0/agent/diagnostic/logs'
- Unauthorized file access attempts in system logs
Network Indicators:
- Unusual outbound traffic patterns from the DSA server
- HTTP requests with suspicious path sequences
SIEM Query:
source="*DSA*" AND (url="*api/appInternals/1.0/agent/diagnostic/logs*" AND (url="*..*" OR url="*../*"))