CVE-2020-11491 in Load Balancer
Summary
by MITRE
Monitoring::Logs in Zen Load Balancer 3.10.1 allows remote authenticated admins to conduct absolute path traversal attacks, as demonstrated by a filelog=/etc/shadow request to index.cgi.
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Analysis
by VulDB Data Team • 05/13/2024
The vulnerability identified as CVE-2020-11491 resides within the Monitoring::Logs functionality of Zen Load Balancer version 3.10.1, representing a critical security flaw that enables remote authenticated administrators to execute absolute path traversal attacks. This issue specifically affects the index.cgi component which processes filelog parameters without adequate input validation or sanitization mechanisms. The vulnerability manifests when an authenticated administrator submits a malicious request containing the parameter filelog=/etc/shadow, allowing unauthorized access to sensitive system files that should remain protected from external inspection. This flaw fundamentally compromises the integrity of the application's file access controls and exposes critical system information to malicious actors who possess administrative credentials.
The technical implementation of this vulnerability stems from improper input validation within the monitoring logs module, where user-supplied parameters are directly incorporated into file system operations without sufficient sanitization or path validation. The absence of proper input filtering allows attackers to manipulate the filelog parameter to traverse the file system hierarchy and access files outside of the intended directory structure. This represents a classic path traversal vulnerability that aligns with CWE-22, which defines the weakness of allowing attackers to access files or directories outside the intended scope through manipulation of file paths. The vulnerability operates at the application layer and can be exploited remotely, requiring only that an attacker possesses valid administrative credentials to the Zen Load Balancer system.
The operational impact of CVE-2020-11491 extends beyond simple information disclosure, as it provides attackers with access to critical system files that may contain sensitive data such as password hashes, configuration settings, or other system information that could facilitate further attacks. The exposure of /etc/shadow file specifically compromises the system's authentication mechanisms, potentially allowing attackers to extract password hashes and perform offline password cracking attacks. Additionally, the vulnerability could enable attackers to access other sensitive files within the system, including configuration files that may contain database credentials, API keys, or other confidential information. This access could lead to privilege escalation, lateral movement within the network, or complete system compromise depending on the system architecture and the attacker's objectives.
Organizations utilizing Zen Load Balancer 3.10.1 should immediately implement mitigation strategies to address this vulnerability. The primary recommended approach involves updating to a patched version of Zen Load Balancer that properly validates and sanitizes user input before processing file system operations. Additionally, administrators should implement network segmentation and access controls to limit the exposure of administrative interfaces to trusted networks only. The principle of least privilege should be enforced by ensuring that administrative accounts have minimal necessary permissions and that regular access reviews are conducted to identify and remove unnecessary administrative access. Implementing web application firewalls and input validation rules can provide additional defense-in-depth measures to detect and block malicious path traversal attempts. Organizations should also conduct comprehensive security assessments to identify other potential vulnerabilities within their load balancer configurations and ensure that proper logging and monitoring mechanisms are in place to detect suspicious activities. This vulnerability demonstrates the importance of implementing proper input validation and access controls as outlined in the mitre ATT&CK framework under the technique of path traversal and privilege escalation.