CVE-2021-26273
📋 TL;DR
CVE-2021-26273 is an incorrect access control vulnerability in NinjaRMM Agent 5.0.909 that allows local privilege escalation. Attackers can exploit this to gain SYSTEM/root privileges on managed endpoints. This affects organizations using vulnerable versions of NinjaRMM for remote monitoring and management.
💻 Affected Systems
- NinjaRMM Agent
📦 What is this software?
Ninjarmm by Ninjarmm
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of managed endpoints with SYSTEM/root privileges, enabling lateral movement, data exfiltration, ransomware deployment, and persistence establishment across the network.
Likely Case
Local privilege escalation on individual endpoints leading to credential theft, malware installation, and bypassing security controls on affected systems.
If Mitigated
Limited impact with proper endpoint security controls, network segmentation, and least privilege principles in place, though local compromise of individual systems remains possible.
🎯 Exploit Status
Exploitation requires local access to the system but is relatively straightforward once initial access is obtained. Public technical details and proof-of-concept information are available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 5.0.909 (specifically fixed in subsequent releases)
Vendor Advisory: https://www.ninjarmm.com/blog/cve-2021-26273-cve-2021-26274/
Restart Required: Yes
Instructions:
1. Log into NinjaRMM dashboard 2. Navigate to device management 3. Check for available agent updates 4. Deploy updated agent version to all endpoints 5. Restart affected systems to complete installation
🔧 Temporary Workarounds
Restrict local access controls
allImplement strict local access controls and least privilege principles to limit initial attack surface
Enhanced endpoint monitoring
allDeploy additional endpoint detection and response (EDR) solutions to detect privilege escalation attempts
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable endpoints from critical systems
- Deploy application whitelisting to prevent execution of unauthorized privilege escalation tools
🔍 How to Verify
Check if Vulnerable:
Check NinjaRMM Agent version on endpoints. On Windows: Check Programs and Features or run 'wmic product get name,version | findstr Ninja'. On macOS/Linux: Check installed packages for ninjarmm-agent version.Check Version:
Windows: 'wmic product get name,version | findstr Ninja' or check Add/Remove Programs. macOS/Linux: Check package manager for ninjarmm-agent version.Verify Fix Applied:
Verify agent version is updated beyond 5.0.909 through NinjaRMM dashboard or local version checks. Confirm no privilege escalation attempts in security logs.📡 Detection & Monitoring
Log Indicators:
- Unusual process creation with SYSTEM privileges from non-admin users
- Access to protected NinjaRMM agent directories/files by non-privileged users
- Security log entries showing privilege escalation attempts
Network Indicators:
- Unusual outbound connections from endpoints after local privilege escalation
- Lateral movement attempts from previously compromised systems
SIEM Query:
Example: (event_id:4688 OR process_creation) AND (parent_process:*ninja* OR process_name:cmd.exe,powershell.exe) AND (integrity_level:System OR user:SYSTEM) AND user!="SYSTEM"🔗 References
- https://improsec.com/tech-blog/privilege-escalation-vulnerability-in-ninjarmm
- https://www.ninjarmm.com
- https://www.ninjarmm.com/blog/cve-2021-26273-cve-2021-26274/
- https://improsec.com/tech-blog/privilege-escalation-vulnerability-in-ninjarmm
- https://www.ninjarmm.com
- https://www.ninjarmm.com/blog/cve-2021-26273-cve-2021-26274/
