CVE-2021-45029
📋 TL;DR
CVE-2021-45029 is a critical vulnerability in Apache ShenYu that allows attackers to inject malicious Groovy or SpEL code, leading to remote code execution. This affects Apache ShenYu versions 2.4.0 and 2.4.1, potentially compromising entire systems. Attackers can execute arbitrary commands with the privileges of the ShenYu application.
💻 Affected Systems
- Apache ShenYu
📦 What is this software?
Shenyu by Apache
Shenyu by Apache
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary commands, steal data, deploy malware, or pivot to other systems in the network.
Likely Case
Remote code execution leading to data theft, service disruption, or deployment of backdoors for persistent access.
If Mitigated
Limited impact with proper network segmentation, minimal privileges, and input validation controls in place.
🎯 Exploit Status
Public exploit details and proof-of-concept code are available in security advisories, making exploitation straightforward for attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.4.2 and later
Vendor Advisory: https://lists.apache.org/thread/3zzmwvg3012tg306x8o893fvdcssx639
Restart Required: Yes
Instructions:
1. Download Apache ShenYu version 2.4.2 or later from official Apache repositories. 2. Stop the current ShenYu service. 3. Replace the vulnerable version with the patched version. 4. Restart the ShenYu service. 5. Verify the update was successful.
🔧 Temporary Workarounds
Disable vulnerable endpoints
allTemporarily disable or restrict access to endpoints that accept Groovy or SpEL expressions if they're not essential for functionality.
# Configure firewall rules to block access to vulnerable endpoints
# Example: iptables -A INPUT -p tcp --dport [shenyu_port] -m string --string "vulnerable_endpoint" --algo bm -j DROP
Network segmentation
allIsolate ShenYu instances from critical systems and implement strict network access controls.
# Implement network segmentation using firewall rules
# Example: iptables -A FORWARD -s [shenyu_ip] -d [critical_system_ip] -j DROP
🧯 If You Can't Patch
- Implement strict input validation and sanitization for all user inputs, especially those processed by Groovy or SpEL engines.
- Deploy web application firewall (WAF) rules to detect and block code injection attempts targeting ShenYu endpoints.
🔍 How to Verify
Check if Vulnerable:
Check the ShenYu version by examining configuration files or running the application with version flag. Vulnerable if version is 2.4.0 or 2.4.1.Check Version:
Check the ShenYu configuration file (usually shenyu-admin or shenyu-bootstrap properties) for version information or run: java -jar shenyu-admin.jar --versionVerify Fix Applied:
Verify the installed version is 2.4.2 or later by checking the application version or configuration files.📡 Detection & Monitoring
Log Indicators:
- Unusual Groovy or SpEL expression execution in logs
- Suspicious command execution patterns
- Unexpected process creation from ShenYu service
Network Indicators:
- Unusual outbound connections from ShenYu instances
- Traffic patterns indicating code injection attempts
SIEM Query:
source="shenyu" AND ("Groovy" OR "SpEL" OR "Expression") AND ("exec" OR "Runtime" OR "ProcessBuilder")🔗 References
- http://www.openwall.com/lists/oss-security/2022/01/25/8
- http://www.openwall.com/lists/oss-security/2022/01/26/1
- https://lists.apache.org/thread/3zzmwvg3012tg306x8o893fvdcssx639
- http://www.openwall.com/lists/oss-security/2022/01/25/8
- http://www.openwall.com/lists/oss-security/2022/01/26/1
- https://lists.apache.org/thread/3zzmwvg3012tg306x8o893fvdcssx639
