CVE-2016-20024: ZKTeco ZKTime.Net Privilege Escalation

CVE-2016-20024 Overview

CVE-2016-20024 is an insecure file permissions vulnerability affecting ZKTeco ZKTime.Net 3.0.1.6, a time and attendance management software solution. The vulnerability allows unprivileged users to escalate privileges by modifying executable files within the application's installation directory. Attackers can exploit world-writable permissions on the ZKTimeNet3.0 directory and its contents to replace executable files with malicious binaries, ultimately achieving privilege escalation on the affected system.

Critical Impact

This vulnerability enables local privilege escalation through insecure file permissions, allowing any unprivileged user with system access to gain elevated privileges by replacing application executables with malicious code.

Affected Products

• ZKTeco ZKTime.Net version 3.0.1.6
• Systems with ZKTimeNet3.0 directory installed with world-writable permissions

Discovery Timeline

• 2026-03-16 - CVE CVE-2016-20024 published to NVD
• 2026-03-16 - Last updated in NVD database

Technical Details for CVE-2016-20024

Vulnerability Analysis

This vulnerability stems from improper file system permission configuration during the installation of ZKTeco ZKTime.Net. The application installs with world-writable permissions on its installation directory (ZKTimeNet3.0) and all contained files, including executable binaries. This insecure configuration violates the principle of least privilege and creates a significant attack surface for local privilege escalation.

When the application service runs with elevated privileges (typically as SYSTEM or an administrative account), any user on the system can replace the legitimate executables with malicious binaries. Upon the next service restart or scheduled execution, the malicious code executes with the elevated privileges of the service account, effectively granting the attacker those same privileges.

The vulnerability is classified under CWE-538 (Insertion of Sensitive Information into Externally-Accessible File or Directory), though it more precisely aligns with insecure file permission issues that enable privilege escalation attacks.

Root Cause

The root cause of this vulnerability is the improper assignment of file system permissions during the ZKTime.Net installation process. The installer configures the ZKTimeNet3.0 directory with overly permissive access controls, granting write access to all users on the system. This configuration error allows any local user to modify application files, including critical executables that run with elevated privileges.

Attack Vector

The attack vector requires local access to the vulnerable system. An attacker with unprivileged user access can perform the following exploitation steps:

1. Identify the ZKTime.Net installation directory with world-writable permissions
2. Create or obtain a malicious executable designed to perform desired privileged actions
3. Replace one of the legitimate application executables with the malicious binary
4. Wait for the ZKTime.Net service to restart or trigger a restart through various means
5. The malicious code executes with the service's elevated privileges

Since no verified code examples are available for this vulnerability, technical details regarding specific exploitation techniques can be found in the referenced security advisories, including the Exploit-DB #40322 entry and the Zero Science Lab advisory ZSL-2016-5360.

Detection Methods for CVE-2016-20024

Indicators of Compromise

• Unexpected modifications to executable files within the ZKTimeNet3.0 installation directory
• Changes to file timestamps or hashes of ZKTime.Net application binaries
• Unusual processes spawned as child processes of ZKTime.Net services
• New or modified scheduled tasks associated with ZKTime.Net components
• Unauthorized privilege escalation events correlated with ZKTime.Net service restarts

Detection Strategies

• Implement file integrity monitoring (FIM) on the ZKTime.Net installation directory to detect unauthorized modifications
• Monitor Windows Security Event Logs for privilege escalation attempts and suspicious service behavior
• Deploy endpoint detection and response (EDR) solutions to identify malicious binaries masquerading as legitimate application files
• Audit file system permissions regularly to identify directories with overly permissive access controls

Monitoring Recommendations

• Configure alerts for any write operations to executable files within the ZKTimeNet3.0 directory
• Monitor service restart events for ZKTime.Net services and correlate with file modification events
• Implement behavioral analysis to detect anomalous process execution patterns from ZKTime.Net services
• Review Windows Event ID 4663 (An attempt was made to access an object) for suspicious file access patterns

How to Mitigate CVE-2016-20024

Immediate Actions Required

• Audit and correct file permissions on the ZKTimeNet3.0 directory to restrict write access to administrators only
• Verify the integrity of all executable files in the ZKTime.Net installation directory against known good hashes
• Consider running the ZKTime.Net service with a dedicated service account with minimal privileges
• Implement application whitelisting to prevent unauthorized executable substitution
• Contact ZKTeco for an updated version or security patch that addresses the insecure default permissions

Patch Information

No official vendor patch information is available in the CVE data. Organizations should contact ZKTeco directly for information regarding security updates that address this vulnerability. Additional technical details and advisories can be found through the VulnCheck ZKTeco Advisory and IBM X-Force Vulnerability 116487.

Workarounds

• Remove write permissions for non-administrative users from the ZKTime.Net installation directory and all subdirectories
• Implement Software Restriction Policies or Windows Defender Application Control to prevent execution of unsigned binaries
• Deploy file integrity monitoring solutions to alert on unauthorized modifications
• Isolate the ZKTime.Net system from untrusted users where possible

# Windows command to restrict permissions on the ZKTimeNet3.0 directory
# Run as Administrator
icacls "C:\Program Files\ZKTimeNet3.0" /inheritance:r /grant:r Administrators:F /grant:r SYSTEM:F
icacls "C:\Program Files\ZKTimeNet3.0\*" /inheritance:e /T