CVE-2008-1524 in ZyNOS
Summary
by MITRE
The SNMP service on ZyXEL Prestige routers, including P-660 and P-661 models with firmware 3.40(AGD.2) through 3.40(AHQ.3), has "public" as its default community for both (1) read and (2) write operations, which allows remote attackers to perform administrative actions via SNMP, as demonstrated by reading the Dynamic DNS service password or inserting an XSS sequence into the system.sysName.0 variable, which is displayed on the System Status page.
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Analysis
by VulDB Data Team • 09/20/2018
The vulnerability identified as CVE-2008-1524 represents a critical security flaw in ZyXEL Prestige routers that affects models P-660 and P-661 with specific firmware versions ranging from 3.40(AGD.2) through 3.40(AHQ.3). This issue stems from the SNMP service implementation where the default community string is set to "public" for both read and write operations, creating an inherent security weakness that exposes administrative functions to unauthorized remote access. The default community string serves as a basic form of authentication within SNMP protocol implementations, and when configured with a well-known default value like "public", it provides attackers with unrestricted access to the router's management interface without requiring additional authentication credentials.
The technical flaw manifests through the SNMP protocol's inherent design weakness where the "public" community string acts as a universal key that grants access to sensitive router configurations and operational parameters. When attackers exploit this vulnerability, they can perform administrative actions including reading critical system information such as Dynamic DNS service passwords, which are typically stored in SNMP accessible variables. The vulnerability is particularly concerning because it allows attackers to inject malicious content directly into system variables, specifically the system.sysName.0 variable that appears on the system status page, enabling cross-site scripting attacks that can compromise the router's web interface and potentially lead to more severe system exploitation.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass full administrative control over affected routers. Remote attackers can leverage the write permissions associated with the default "public" community string to modify router configurations, inject malicious code, and potentially establish persistent access points within network environments. The ability to insert XSS sequences into the system.sysName.0 variable creates a particularly dangerous attack vector as it allows for client-side code execution when the system status page is viewed by legitimate users, potentially leading to session hijacking, data theft, or further network compromise. This vulnerability effectively undermines the router's security posture and compromises the integrity of the network infrastructure it protects.
Organizations affected by this vulnerability should implement immediate mitigation strategies including changing the default SNMP community strings to strong, unique values and disabling SNMP access when not required for legitimate network management purposes. Network segmentation and access control measures should be implemented to limit exposure of these devices to unauthorized networks. The vulnerability aligns with CWE-79 Cross-site Scripting and CWE-312 Cleartext Storage of Sensitive Information, representing a classic case of insecure default configurations that violates fundamental security principles. From an ATT&CK framework perspective, this vulnerability maps to T1071.004 Application Layer Protocol and T1059.001 Command and Scripting Interpreter, as attackers can leverage the SNMP interface to execute commands and establish persistence. The vulnerability demonstrates how default configurations that prioritize usability over security can create significant risks, emphasizing the importance of implementing security by design principles in network infrastructure devices.