CVE-2020-9493
📋 TL;DR
CVE-2020-9493 is a critical deserialization vulnerability in Apache Chainsaw that allows remote attackers to execute arbitrary code by sending specially crafted data. This affects all Apache Chainsaw versions before 2.1.0. Organizations using vulnerable versions of this log viewer tool are at risk of complete system compromise.
💻 Affected Systems
- Apache Chainsaw
📦 What is this software?
Chainsaw by Apache
Log4j by Apache
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to full system compromise, data exfiltration, ransomware deployment, or lateral movement across the network.
Likely Case
Attackers gain initial foothold on vulnerable systems, install backdoors, and establish persistence for further attacks.
If Mitigated
With proper network segmentation and least privilege, impact limited to isolated logging systems with minimal sensitive data.
🎯 Exploit Status
Exploitation is straightforward as it involves sending malicious serialized data to the vulnerable component.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.1.0 and later
Vendor Advisory: https://lists.apache.org/thread.html/r50d389c613ba6062a26aa57e163c09bfee4ff2d95d67331d75265b83%40%3Cannounce.apache.org%3E
Restart Required: Yes
Instructions:
1. Download Apache Chainsaw 2.1.0 or later from the official Apache website. 2. Stop the current Chainsaw instance. 3. Install the new version. 4. Restart Chainsaw with the updated version.
🔧 Temporary Workarounds
Network Access Restriction
linuxRestrict network access to Apache Chainsaw to only trusted IP addresses or internal networks.
# Use firewall rules to restrict access
iptables -A INPUT -p tcp --dport [CHAINSAW_PORT] -s [TRUSTED_IP] -j ACCEPT
iptables -A INPUT -p tcp --dport [CHAINSAW_PORT] -j DROP
Disable Remote Access
allConfigure Chainsaw to only accept local connections if remote access is not required.
# Edit Chainsaw configuration to bind to localhost only
bind_address=127.0.0.1
🧯 If You Can't Patch
- Isolate the vulnerable system in a separate network segment with strict firewall rules
- Implement application-level controls to filter or block serialized data inputs
🔍 How to Verify
Check if Vulnerable:
Check the Apache Chainsaw version. If it's below 2.1.0, the system is vulnerable.Check Version:
Check the application interface or configuration files for version information. On Linux: grep -i version /path/to/chainsaw/config/*Verify Fix Applied:
Verify the installed version is 2.1.0 or higher and test that the application functions normally.📡 Detection & Monitoring
Log Indicators:
- Unusual deserialization errors in Chainsaw logs
- Unexpected process execution from Chainsaw context
- Network connections from Chainsaw to suspicious external IPs
Network Indicators:
- Unusual traffic patterns to/from Chainsaw port
- Large serialized data payloads sent to Chainsaw
SIEM Query:
source="chainsaw.log" AND ("deserialization" OR "ClassNotFoundException" OR "InvalidClassException")🔗 References
- http://www.openwall.com/lists/oss-security/2021/06/16/1
- http://www.openwall.com/lists/oss-security/2022/01/18/5
- https://lists.apache.org/thread.html/r50d389c613ba6062a26aa57e163c09bfee4ff2d95d67331d75265b83%40%3Cannounce.apache.org%3E
- https://www.openwall.com/lists/oss-security/2021/06/16/1
- http://www.openwall.com/lists/oss-security/2021/06/16/1
- http://www.openwall.com/lists/oss-security/2022/01/18/5
- https://lists.apache.org/thread.html/r50d389c613ba6062a26aa57e163c09bfee4ff2d95d67331d75265b83%40%3Cannounce.apache.org%3E
- https://www.openwall.com/lists/oss-security/2021/06/16/1
