CVE-2021-4406
📋 TL;DR
This vulnerability allows authenticated attackers to create alerts that trigger stored cross-site scripting (XSS) attacks, which can lead to remote command execution as root. It affects OSNexus QuantaStor systems. Attackers need valid credentials to exploit this vulnerability.
💻 Affected Systems
- OSNexus QuantaStor
📦 What is this software?
Quantastor by Osnexus
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with root-level command execution, allowing data theft, system modification, or deployment of persistent backdoors.
Likely Case
Unauthorized command execution leading to data exfiltration, privilege escalation, or lateral movement within the network.
If Mitigated
Limited impact if proper input validation and output encoding are implemented, restricting attackers to authenticated session hijacking only.
🎯 Exploit Status
Exploit requires authenticated access but follows simple steps with a published proof-of-concept; attackers can execute arbitrary commands as root.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in references, but patches are available from OSNexus
Vendor Advisory: https://www.osnexus.com/products/software-defined-storage
Restart Required: Yes
Instructions:
1. Check for available updates from OSNexus. 2. Apply the security patch for QuantaStor. 3. Restart the QuantaStor service or system as required.
🔧 Temporary Workarounds
Disable Alert Manager Webhook Functionality
linuxTemporarily disable or restrict webhook creation in the alert manager to prevent exploitation.
Specific commands not provided; configure via QuantaStor web interface or configuration files.
Implement Input Validation
linuxAdd server-side validation to sanitize webhook URL inputs and reject malicious payloads.
Configuration-dependent; modify QuantaStor application code or settings.
🧯 If You Can't Patch
- Restrict access to the QuantaStor management interface to trusted networks only.
- Implement strong authentication controls and monitor for unusual alert creation activities.
🔍 How to Verify
Check if Vulnerable:
Check if your QuantaStor version is unpatched by comparing with the latest secure version from OSNexus; test by attempting the POC in a controlled environment.Check Version:
Use QuantaStor web interface or CLI commands specific to the system to check the current software version.Verify Fix Applied:
After patching, verify that the POC no longer executes commands; check version number against patched releases.📡 Detection & Monitoring
Log Indicators:
- Unusual alert creations, webhook entries with suspicious characters or commands in QuantaStor logs.
Network Indicators:
- Unexpected outbound connections from the QuantaStor system post-alert trigger.
SIEM Query:
Search for events related to 'alert creation', 'webhook', or command execution in system logs from QuantaStor hosts.🔗 References
- https://csirt.divd.nl/CVE-2021-4406
- https://csirt.divd.nl/DIVD-2021-00020/
- https://www.osnexus.com/products/software-defined-storage
- https://csirt.divd.nl/CVE-2021-4406
- https://www.divd.nl/DIVD-2021-00020
- https://www.osnexus.com/products/software-defined-storage
- https://csirt.divd.nl/cves/CVE-2021-4406/
