CVE-2021-26558
📋 TL;DR
CVE-2021-26558 is a deserialization vulnerability in Apache ShardingSphere-UI that allows attackers to inject malicious external resources through untrusted data. This can lead to remote code execution on affected systems. The vulnerability affects Apache ShardingSphere-UI versions 4.1.1 through 4.x, specifically all versions before 5.0.0.
💻 Affected Systems
- Apache ShardingSphere-UI
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with full system compromise, allowing attackers to execute arbitrary commands, steal data, or deploy ransomware.
Likely Case
Server compromise leading to data exfiltration, lateral movement within the network, or deployment of backdoors.
If Mitigated
Limited impact if proper network segmentation and least privilege principles are implemented, potentially containing the attack to the affected service.
🎯 Exploit Status
Deserialization vulnerabilities are commonly exploited and weaponized. Public proof-of-concept exists in security advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.0.0
Vendor Advisory: https://lists.apache.org/thread/4gzkm1zb6c97v9gl8lcz8ll5xr8o484c
Restart Required: Yes
Instructions:
1. Upgrade Apache ShardingSphere-UI to version 5.0.0 or later. 2. Download from official Apache repository. 3. Replace existing installation. 4. Restart the ShardingSphere-UI service.
🔧 Temporary Workarounds
Network Isolation
linuxRestrict network access to ShardingSphere-UI to trusted IP addresses only.
iptables -A INPUT -p tcp --dport [UI_PORT] -s [TRUSTED_IP] -j ACCEPT
iptables -A INPUT -p tcp --dport [UI_PORT] -j DROP
Disable UI Component
linuxTemporarily disable ShardingSphere-UI if not essential for operations.
systemctl stop shardingsphere-ui
systemctl disable shardingsphere-ui
🧯 If You Can't Patch
- Implement strict network segmentation to isolate ShardingSphere-UI from critical systems.
- Deploy web application firewall (WAF) with deserialization attack detection rules.
🔍 How to Verify
Check if Vulnerable:
Check ShardingSphere-UI version: grep 'version' /path/to/shardingsphere-ui/conf/application.properties or check UI interface.Check Version:
grep 'shardingsphere.ui.version' /path/to/shardingsphere-ui/conf/application.propertiesVerify Fix Applied:
Verify version is 5.0.0 or higher using same method as checking vulnerability.📡 Detection & Monitoring
Log Indicators:
- Unusual deserialization errors in application logs
- Unexpected external resource loading
- Suspicious Java class loading
Network Indicators:
- Unusual outbound connections from ShardingSphere-UI server
- Traffic to known malicious domains
SIEM Query:
source="shardingsphere-ui" AND (error OR exception) AND (deserialization OR ClassNotFoundException)