CVE-2021-21513
📋 TL;DR
CVE-2021-21513 is an authentication bypass vulnerability in Dell EMC OpenManage Server Administrator (OMSA) that allows remote unauthenticated attackers to gain administrative access to affected systems. This affects Windows installations with Distributed Web Server (DWS) enabled. Organizations using OMSA for server management are at risk of complete system compromise.
💻 Affected Systems
- Dell EMC OpenManage Server Administrator (OMSA)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote attacker gains full administrative control over the server, enabling data theft, ransomware deployment, lateral movement, and complete system compromise.
Likely Case
Attackers exploit the vulnerability to gain administrative access, install malware, exfiltrate sensitive data, and use the system as a foothold for further attacks.
If Mitigated
With proper network segmentation and access controls, impact is limited to the management interface, though administrative access still poses significant risk.
🎯 Exploit Status
Public proof-of-concept code exists, making exploitation straightforward for attackers with network access to vulnerable systems.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: OMSA 9.5.0.0 or later with security updates
Restart Required: Yes
Instructions:
1. Download the latest OMSA update from Dell Support. 2. Apply the security update (DSA-2021-040). 3. Restart the system to complete installation. 4. Verify the update was successful.
🔧 Temporary Workarounds
Disable Distributed Web Server (DWS)
windowsDisable the vulnerable DWS component if not required for operations
Open OMSA Configuration → Web Server → Disable Distributed Web Server
Network Access Control
allRestrict network access to OMSA management interface
Use firewall rules to block external access to OMSA ports (typically 1311, 1312)
🧯 If You Can't Patch
- Disable Distributed Web Server (DWS) component immediately
- Implement strict network segmentation and firewall rules to isolate OMSA management interfaces
🔍 How to Verify
Check if Vulnerable:
Check if OMSA version is 9.5 with DWS enabled. Review OMSA configuration for DWS status.Check Version:
Open OMSA → Help → About to check versionVerify Fix Applied:
Verify OMSA version is 9.5.0.0 or later and confirm DWS is either disabled or patched.📡 Detection & Monitoring
Log Indicators:
- Unauthenticated access attempts to OMSA web interface
- Unusual administrative actions from unexpected IPs
- Authentication bypass patterns in web server logs
Network Indicators:
- Unusual traffic to OMSA ports (1311, 1312) from external sources
- Administrative API calls without authentication
SIEM Query:
source="omsa_logs" AND (event="authentication_bypass" OR status="401" followed by admin_access)🔗 References
- https://www.dell.com/support/kbdoc/en-us/000183670/dsa-2021-040-dell-emc-openmanage-server-administrator-omsa-security-update-for-multiple-vulnerabilities
- https://www.tenable.com/security/research/tra-2021-07
- https://www.dell.com/support/kbdoc/en-us/000183670/dsa-2021-040-dell-emc-openmanage-server-administrator-omsa-security-update-for-multiple-vulnerabilities
- https://www.tenable.com/security/research/tra-2021-07
