CVE-2021-21726 in ZXONE 9700
Summary
by MITRE • 03/13/2021
Some ZTE products have an input verification vulnerability in the diagnostic function interface. Due to insufficient verification of some parameters input by users, an attacker with high privileges can cause process exception by repeatedly inputting illegal parameters. This affects:
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Analysis
by VulDB Data Team • 04/01/2021
The vulnerability identified as CVE-2021-21726 represents a critical input validation flaw within the diagnostic function interface of various ZTE network equipment products. This weakness stems from inadequate parameter validation mechanisms that fail to properly sanitize or verify user inputs before processing them within the system's diagnostic subsystem. The vulnerability specifically manifests when the diagnostic interface receives malformed or malicious input parameters that are not adequately filtered or checked for legitimacy. Security researchers have determined that this issue exists in multiple ZTE device models including but not limited to routers, switches, and network management systems that incorporate diagnostic functionalities.
The technical nature of this vulnerability aligns with CWE-20, which describes improper input validation as a fundamental weakness in software design where applications fail to properly validate or sanitize user-supplied data. The flaw operates through a process of parameter manipulation where an attacker with high privileges can exploit the insufficient validation controls by repeatedly submitting illegal parameters to the diagnostic interface. This exploitation pattern creates a condition where the system's diagnostic process becomes unstable or crashes due to the malformed inputs not being properly handled by the application's input validation routines. The vulnerability essentially allows for a form of process disruption or denial of service through carefully crafted input sequences that the system cannot properly process.
From an operational perspective, this vulnerability presents significant risks to network infrastructure stability and availability. The requirement for high privileges to exploit this vulnerability means that it is not easily accessible to casual attackers, but rather represents a serious concern for privileged users who may have malicious intent or for situations where privilege escalation occurs through other means. The impact of exploitation includes potential service disruption, process crashes, and in some cases, system instability that could affect network operations. Organizations using affected ZTE equipment face potential downtime and operational interruptions if this vulnerability is successfully exploited, particularly in mission-critical network environments where diagnostic functionality is frequently used for troubleshooting and maintenance operations.
The attack surface for this vulnerability extends across various ZTE network equipment platforms that implement diagnostic interfaces, making it a widespread concern for network administrators and security teams. The ATT&CK framework categorizes this type of vulnerability under privilege escalation and denial of service tactics, where an attacker with sufficient privileges can leverage input validation weaknesses to disrupt system operations. Mitigation strategies should focus on implementing proper input validation controls, including parameter sanitization, input length restrictions, and comprehensive error handling mechanisms within the diagnostic interface. Network security teams should also consider implementing monitoring and logging controls to detect unusual diagnostic interface activity that might indicate exploitation attempts. Additionally, regular firmware updates and patches provided by ZTE should be applied promptly to address this vulnerability and maintain the security posture of affected network infrastructure.