CVE-2026-59783 in Zabbix
Summary
by MITRE • 10/05/2026
The Zabbix Server/Proxy has a vulnerability where binary items can crash the Server/Proxy on certain NULL byte input leading to potential loss of availability. This only affects deployments where MySQL/MariaDB database is used as the Zabbix database.
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Analysis
by VulDB Data Team • 10/05/2026
Zabbix, an open-source enterprise-class monitoring solution widely deployed for infrastructure and application performance tracking, contains a critical vulnerability affecting its Server and Proxy components when utilizing MySQL or MariaDB databases. The flaw resides in the handling of binary data items within the system's input processing logic. Specifically, the software fails to adequately sanitize or validate NULL bytes embedded within binary item inputs before they are processed by the database layer. This lack of proper boundary checking allows a specially crafted payload containing null characters to bypass expected validation routines and trigger an unhandled exception during query execution or data parsing operations.
The technical root cause is classified under CWE-20, Improper Input Validation, as the application does not correctly filter out dangerous input sequences that can disrupt normal program flow. When a NULL byte is introduced into binary item fields, it interferes with string termination expectations in underlying C/C++ libraries or database driver interfaces commonly used by Zabbix to communicate with MySQL/MariaDB instances. This interference leads to memory corruption or segmentation faults within the server process, causing immediate and uncontrolled termination of the affected service thread or the entire daemon depending on the specific configuration and load conditions at the time of exploitation.
From an operational perspective, this vulnerability poses a severe risk to availability, aligning with CWE-400 Uncontrolled Resource Consumption in terms of impact severity due to system crash. An authenticated attacker who has access to create or modify monitoring items can exploit this flaw by submitting malicious binary data containing NULL bytes. The resulting denial of service disrupts the continuous collection and processing of metrics, leading to gaps in observability that may obscure ongoing infrastructure issues or security incidents. In high-availability clusters where Zabbix Server acts as a central point for multiple proxies, crashing one node can trigger failover events that further strain system resources and complicate incident response efforts during an active attack window.
Mitigation strategies must focus on immediate patching to the latest stable release of Zabbix which includes fixes for input validation in binary item handling. Administrators should verify their database backend is strictly MySQL or MariaDB, as this vulnerability does not impact PostgreSQL or Oracle deployments due to differences in how those drivers handle string termination and null bytes. Additionally, implementing strict access controls on the Zabbix web interface and API ensures that only trusted personnel can create or modify monitoring items, reducing the attack surface for authenticated exploitation. Network-level segmentation should also be enforced to limit direct internet-facing exposure of management interfaces until patches are applied.
This vulnerability is relevant to ATT&CK technique T1499 Endpoint Denial of Service, as it involves leveraging a software flaw to disrupt service availability rather than compromising confidentiality or integrity directly. Security teams should monitor logs for unexpected Zabbix server restarts or crash dumps that correlate with recent item creation activities involving binary data fields. Regular auditing of input validation mechanisms across all monitored applications is recommended to prevent similar flaws from being introduced in custom integrations or scripts interacting with the monitoring platform.