CVE-2021-26620
📋 TL;DR
This vulnerability in iptime NAS2dual devices allows remote attackers to bypass authentication mechanisms and access shared folders or change user passwords. Attackers can steal sensitive information stored on the NAS server. All users of affected iptime NAS2dual devices are at risk.
💻 Affected Systems
- iptime NAS2dual
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of all data stored on the NAS, including sensitive documents, backups, and credentials, potentially leading to data theft, ransomware deployment, or lateral movement into connected networks.
Likely Case
Unauthorized access to shared folders containing sensitive information, password changes locking legitimate users out of their accounts, and potential data exfiltration.
If Mitigated
Limited impact with proper network segmentation and access controls, though the vulnerability still exists at the device level.
🎯 Exploit Status
The vulnerability involves improper authentication checks, making exploitation straightforward for attackers who can reach the device.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Latest firmware version from iptime (check vendor site for specific version)
Vendor Advisory: https://www.iptime.com/iptime/?page_id=41&uid=100&mod=document
Restart Required: Yes
Instructions:
1. Log into iptime NAS2dual web interface. 2. Navigate to System > Firmware Update. 3. Check for and apply the latest firmware. 4. Reboot the device after update completes.
🔧 Temporary Workarounds
Disable Remote Access
allBlock external access to the NAS management interface and file sharing services
Configure firewall rules to block inbound traffic to NAS ports (typically 80, 443, 445, 2049)
Network Segmentation
allIsolate NAS device to trusted network segments only
Place NAS on separate VLAN with strict access controls
🧯 If You Can't Patch
- Immediately disconnect the NAS from internet-facing networks
- Implement strict network access controls allowing only trusted IP addresses to connect
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface under System > Firmware Information. If version predates CVE-2021-26620 fix, device is vulnerable.Check Version:
Not applicable - check via web interface at http://[NAS-IP]/system/firmware.aspVerify Fix Applied:
After updating firmware, verify version matches latest release from vendor and test authentication requirements for shared folder access.📡 Detection & Monitoring
Log Indicators:
- Failed authentication attempts followed by successful access to shared folders
- Unauthorized password change requests in system logs
- Access to sensitive directories from unexpected IP addresses
Network Indicators:
- Unusual SMB/NFS traffic patterns
- Authentication bypass attempts to NAS management interface
- Data exfiltration from NAS to external IPs
SIEM Query:
source="nas_logs" AND (event_type="auth_bypass" OR (auth_result="success" AND auth_method="none") OR file_access="unauthorized")