CVE-2021-27893
📋 TL;DR
This vulnerability allows local privilege escalation on Windows systems running SSH Tectia Client and Server in nonstandard conditions. It affects ConnectSecure on Windows, enabling attackers with local access to elevate privileges to SYSTEM level. Only Windows installations with specific nonstandard configurations are vulnerable.
💻 Affected Systems
- SSH Tectia Client
- SSH Tectia Server
- ConnectSecure
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Local attacker gains SYSTEM privileges, enabling complete system compromise, credential theft, persistence establishment, and lateral movement capabilities.
Likely Case
Local user or malware with initial access escalates to administrative privileges, allowing installation of additional malware, disabling security controls, and accessing sensitive data.
If Mitigated
With proper access controls and monitoring, impact is limited to isolated systems; privilege escalation attempts are detected and contained.
🎯 Exploit Status
Requires local access and specific nonstandard configurations. No public exploit code has been released as of available information.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.4.19
Vendor Advisory: https://info.ssh.com/tectia-vulnerability-cve-2021-27893
Restart Required: Yes
Instructions:
1. Download SSH Tectia version 6.4.19 or later from SSH.com. 2. Backup current configuration. 3. Install the update following vendor instructions. 4. Restart affected services or system. 5. Verify successful update.
🔧 Temporary Workarounds
Restrict Local Access
windowsLimit local user access to systems running vulnerable SSH Tectia installations
Review Configuration
windowsAudit and revert any nonstandard SSH Tectia configurations to default settings
🧯 If You Can't Patch
- Implement strict local access controls and monitoring on affected systems
- Isolate vulnerable systems from critical network segments and data
🔍 How to Verify
Check if Vulnerable:
Check SSH Tectia version on Windows systems: version must be 6.4.19 or higher to be patchedCheck Version:
Check SSH Tectia application properties or documentation for version informationVerify Fix Applied:
Verify installed version is 6.4.19 or later and review configuration for nonstandard settings📡 Detection & Monitoring
Log Indicators:
- Unusual privilege escalation attempts
- SSH Tectia service restarts or failures
- Unexpected local user activity
Network Indicators:
- Unusual SSH connections from localhost
- Anomalous authentication patterns
SIEM Query:
Search for events related to SSH Tectia service modifications, privilege escalation attempts, or unusual local user activity on Windows systems