CVE-2026-23938 in Zabbix
Summary
by MITRE • 08/18/2026
An authenticated administrator is able to crash Zabbix server or proxy by creating specifically crafted preprocessing/script item JavaScript scripts, leading to potential denial of service.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified in the Zabbix monitoring platform represents a critical security flaw within its script execution engine, specifically affecting components responsible for processing and executing custom JavaScript code used in data preprocessing and automated actions. This issue arises from insufficient input validation or resource management controls when handling scripts created by authenticated administrators. While administrative access is required to exploit this condition, which inherently limits the attack surface compared to unauthenticated vulnerabilities, it remains a significant risk because system compromise often begins with privileged account abuse or credential theft. The core technical flaw lies in how the Zabbix server and proxy handle the execution context of these scripts, allowing specifically crafted inputs to trigger conditions that exhaust system resources such as memory or CPU cycles, ultimately causing the service process to terminate unexpectedly.
From a technical perspective, this vulnerability is classified under CWE-400, which denotes Uncontrolled Resource Consumption, often leading directly to Denial of Service (DoS) scenarios. When an administrator creates a preprocessing item with a script containing maliciously crafted JavaScript logic, such as infinite loops or excessive memory allocation patterns that bypass internal safeguards, the Zabbix engine attempts to execute this code during data processing cycles. The execution environment fails to properly isolate or limit the computational resources available to individual scripts. Consequently, the server or proxy process becomes unresponsive or crashes entirely, disrupting the collection of metrics and alerts for all monitored hosts under its jurisdiction. This behavior aligns with MITRE ATT&CK technique T1499, Endpoint Denial of Service, where an adversary disrupts service availability by exploiting software weaknesses to consume critical resources.
The operational impact of this vulnerability is severe due to the central role Zabbix plays in enterprise infrastructure monitoring. A successful exploitation results in a complete outage of the monitoring system, leaving administrators blind to server health, network performance, and application status. This loss of visibility can mask other ongoing attacks or failures within the monitored environment. Furthermore, frequent crashes may lead to data loss if historical metric storage is interrupted during the crash sequence. For organizations relying on Zabbix for SLA compliance and incident response, this downtime directly impacts operational continuity and decision-making capabilities. The requirement for authentication means that an attacker must first gain valid administrative credentials through phishing, credential stuffing, or other initial access vectors before they can leverage this flaw to cause disruption.
Mitigation strategies should focus primarily on strict privilege management and input sanitization within the application configuration. Administrators should adhere to the principle of least privilege by ensuring that only essential personnel have access to create or modify scripts in preprocessing items. Implementing multi-factor authentication for administrative accounts significantly reduces the risk of credential compromise leading to this exploitation. Additionally, Zabbix administrators should review any custom JavaScript code used in their environment for potential resource-intensive patterns and consider implementing external sandboxing solutions if available in future versions. Keeping the Zabbix software updated is crucial as vendors typically release patches that address such logic flaws by enforcing stricter limits on script execution time and memory usage. Monitoring system logs for unusual spikes in CPU or memory consumption associated with script processing can also help detect attempted exploitation attempts early.