CVE-2021-30181
📋 TL;DR
Apache Dubbo prior to versions 2.6.9 and 2.7.9 contains a remote code execution vulnerability in its Script routing feature. Attackers can exploit this by submitting malicious routing rules that get executed by the ScriptEngine, potentially allowing arbitrary code execution on affected servers. Organizations using vulnerable Dubbo versions with Script routing enabled are affected.
💻 Affected Systems
- Apache Dubbo
📦 What is this software?
Dubbo by Apache
Dubbo by Apache
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise allowing attackers to execute arbitrary commands, access sensitive 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 cryptocurrency miners or ransomware.
If Mitigated
Limited impact if Script routing is disabled or proper input validation and sandboxing are implemented.
🎯 Exploit Status
Exploitation requires sending specially crafted routing rules to vulnerable endpoints. The vulnerability is in the ScriptEngine execution of user-supplied scripts.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.6.9 and 2.7.9
Vendor Advisory: https://lists.apache.org/thread.html/re22410dc704a09bc7032ddf15140cf5e7df3e8ece390fc9032ff5587%40%3Cdev.dubbo.apache.org%3E
Restart Required: Yes
Instructions:
1. Upgrade Apache Dubbo to version 2.6.9 or 2.7.9 or later. 2. Update dependencies to use the patched version. 3. Restart all Dubbo services. 4. Verify the upgrade was successful.
🔧 Temporary Workarounds
Disable Script Routing
allDisable the Script routing feature if not required for your use case.
Modify Dubbo configuration to remove or disable script routing rules
Network Segmentation
allRestrict access to Dubbo services to trusted networks only.
Configure firewall rules to limit Dubbo port access (default 20880)
🧯 If You Can't Patch
- Disable Script routing feature entirely in Dubbo configuration
- Implement strict input validation and sanitization for all routing rule inputs
🔍 How to Verify
Check if Vulnerable:
Check Dubbo version and configuration. If using version <2.6.9 or <2.7.9 with Script routing enabled, you are vulnerable.Check Version:
Check application dependencies or run: java -jar your-dubbo-app.jar --versionVerify Fix Applied:
Verify Dubbo version is 2.6.9+ or 2.7.9+ and test that Script routing no longer executes arbitrary code.📡 Detection & Monitoring
Log Indicators:
- Unusual script execution in routing logs
- Errors related to ScriptEngine execution
- Suspicious routing rule submissions
Network Indicators:
- Unusual traffic to Dubbo ports (default 20880) with script-like payloads
- Requests containing JavaScript or other scripting language code
SIEM Query:
source="dubbo" AND ("ScriptEngine" OR "routing.script" OR "javascript:")