CVE-2018-14056 in ZNC
Summary
by MITRE
ZNC before 1.7.1-rc1 is prone to a path traversal flaw via ../ in a web skin name to access files outside of the intended skins directories.
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Analysis
by VulDB Data Team • 04/09/2023
The vulnerability identified as CVE-2018-14056 affects ZNC versions prior to 1.7.1-rc1 and represents a critical path traversal flaw that undermines the web interface security model. This vulnerability specifically targets the web skin handling mechanism within the ZNC application, which is a popular IRC bouncer software used by many organizations for maintaining persistent IRC connections. The flaw allows attackers to manipulate the web skin name parameter by injecting ../ sequences that can traverse the directory structure beyond the intended skins directories.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the web interface component of ZNC. When users specify a web skin name through the web interface, the application fails to properly validate or sanitize the input string before using it to construct file paths. This oversight enables malicious actors to craft requests containing directory traversal sequences that bypass the intended directory boundaries. The vulnerability operates at the application level where user-supplied input is directly incorporated into file system operations without adequate security controls.
The operational impact of this vulnerability is significant as it allows remote attackers to access arbitrary files on the system where ZNC is running. An attacker could potentially retrieve sensitive configuration files, user credentials, or other confidential data that may be stored within the application's file system. The vulnerability is particularly dangerous because it can be exploited remotely without requiring authentication, making it an attractive target for automated attacks. The scope of the compromise extends beyond just the web interface to potentially include any files accessible through the application's file system permissions.
This vulnerability maps directly to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal. The attack pattern aligns with techniques documented in the ATT&CK framework under T1059.007 for command and scripting interpreter and T1566.001 for credential access through exploitation of vulnerabilities. The flaw represents a classic example of how insufficient input validation can lead to arbitrary file access, a common theme in web application security vulnerabilities.
The recommended mitigation strategy involves upgrading to ZNC version 1.7.1-rc1 or later, which includes proper input validation and sanitization for web skin names. Organizations should also implement additional security controls such as restricting web interface access to trusted networks, implementing proper file system permissions, and monitoring for suspicious directory traversal attempts. Network segmentation and web application firewalls can provide additional layers of protection. Regular security audits and vulnerability assessments should be conducted to identify similar issues in other components of the system infrastructure.