URGENT PATCH ALERT • LPE

      CRITICAL Zabbix Flaw: Agent and Agent 2 Vulnerability Lets Attackers ESCALATE PRIVILEGES on Windows    

By CyberDudeBivash • October 06, 2025 • Urgent Security Directive

 cyberdudebivash.com |       cyberbivash.blogspot.com 

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Disclosure: This is a security advisory for Zabbix users and Windows administrators. It contains affiliate links to relevant enterprise security solutions. Your support helps fund our independent research.

 Emergency Guide: Table of Contents 

1. Chapter 1: Threat Analysis — The Unquoted Service Path LPE (CVE-2025-27238)
2. Chapter 2: The Kill Chain — From Low-Privilege User to Full Admin
3. Chapter 3: The Defender’s Playbook — Patching and Verifying the Fix
4. Chapter 4: The Strategic Response — The Importance of Secure Configurations

Chapter 1: Threat Analysis — The Unquoted Service Path LPE (CVE-2025-27238)

A critical Local Privilege Escalation (LPE) vulnerability has been discovered in the Zabbix Agent and Zabbix Agent 2 for Windows. This flaw, tracked as **CVE-2025-27238**, is a classic but severe configuration mistake: an **Unquoted Service Path**. Because the Zabbix Agent service runs with the highest privileges (`NT AUTHORITY\SYSTEM`), this flaw provides a direct and reliable path for any local low-privileged user to gain complete administrative control of the server.

Chapter 2: The Kill Chain — From Low-Privilege User to Full Admin

The exploit takes advantage of how the Windows Service Control Manager interprets file paths that contain spaces.

The Exploit:

1. **The Flaw:** The Zabbix Agent installer registers the service path without quotation marks, e.g., `C:\Program Files\Zabbix Agent\zabbix_agentd.exe`.
2. **The Ambiguity:** When the service starts, Windows tries to interpret this path. It will first look for `C:\Program.exe`. If that doesn’t exist, it will look for `C:\Program Files\Zabbix.exe`, and so on.
3. **The Exploit:** An attacker with a low-privileged account (who, on a misconfigured server, may have write permissions to `C:\`) can place a malicious file named `Program.exe` in the root directory.
4. **The Takeover:** The next time the server reboots or the Zabbix Agent service is restarted, the Windows Service Manager will find and execute the attacker’s `C:\Program.exe` with `SYSTEM` privileges instead of the real agent. The attacker now owns the server.

Chapter 3: The Defender’s Playbook — Patching and Verifying the Fix

Immediate action is required on all of your monitored Windows endpoints.

Step 1: PATCH ALL WINDOWS AGENTS

The vendor has released a new version of the Zabbix Agent that correctly quotes the service path during installation. You must **update the Zabbix Agent software on every single Windows server and workstation** you monitor. Simply updating the Zabbix Server will not fix this.

Step 2: Manually Verify and Fix (Optional but Recommended)

You can check if your service is vulnerable. Open a command prompt as Administrator and run:`sc qc “Zabbix Agent”`

Look at the `BINARY_PATH_NAME`. If it does not have quotes around it, it is vulnerable. You can fix it manually with this command:

sc config "Zabbix Agent" binPath= "\"C:\Program Files\Zabbix Agent\zabbix_agentd.exe\""

Step 3: Hunt for Other Unquoted Service Paths

This is a common misconfiguration. Use PowerShell or your EDR to hunt for this flaw in other applications on your servers:

wmic service get name,displayname,pathname,startmode | findstr /i "auto" | findstr /i /v """

This command lists all auto-start services with unquoted paths, which should all be investigated and remediated.

Chapter 4: The Strategic Response — The Importance of Secure Configurations

This vulnerability is a textbook example of a simple development mistake leading to a critical security flaw. It highlights the absolute necessity of a robust server hardening and configuration management program. Attackers are constantly looking for these basic, easy-to-exploit configuration errors.

A mature security program doesn’t just rely on patching vulnerabilities; it proactively hardens systems to eliminate entire classes of bugs. This includes enforcing secure defaults, running configuration scanners, and having a powerful **EDR solution** to detect the post-exploitation activity that follows a privilege escalation event.

 Detect the Post-Exploitation Phase: A modern security solution like **Kaspersky Endpoint Security for Windows Server** is your essential safety net. It can detect the attacker’s actions *after* they’ve gained SYSTEM privileges, such as attempting to dump credentials with Mimikatz or moving laterally to other servers.  

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About the Author

CyberDudeBivash is a cybersecurity strategist with 15+ years in Windows security, incident response, and threat hunting, advising CISOs across APAC.  

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