CVE-2013-0337 in nginx
Summary
by MITRE
The default configuration of nginx, possibly 1.3.13 and earlier, uses world-readable permissions for the (1) access.log and (2) error.log files, which allows local users to obtain sensitive information by reading the files.
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Analysis
by VulDB Data Team • 01/09/2022
The vulnerability identified as CVE-2013-0337 represents a critical configuration flaw in the nginx web server software that affects versions 1.3.13 and earlier. This issue stems from the default installation settings where log files are created with overly permissive world-readable permissions, creating an information disclosure vulnerability that can be exploited by local attackers. The vulnerability specifically impacts two critical log files: access.log and error.log, which are essential components for monitoring and security auditing of web server operations.
The technical flaw manifests through improper file permission handling during the nginx installation process, where the default configuration does not enforce restrictive access controls on log files. When nginx creates these log files, it assigns permissions that allow any user on the system to read their contents, effectively exposing sensitive information to unauthorized local users. The access.log file typically contains records of all client requests including user agents, IP addresses, and requested resources, while the error.log file may reveal system errors, configuration issues, and potentially sensitive operational details that could aid attackers in planning further exploitation attempts.
The operational impact of this vulnerability extends beyond simple information disclosure, as the exposed log data can provide attackers with valuable intelligence for subsequent attacks. Local users who gain read access to these log files can obtain detailed information about web server activity, including potential security misconfigurations, application vulnerabilities, and user behavior patterns that could be leveraged for privilege escalation or lateral movement within the network. This vulnerability directly aligns with CWE-732, which addresses improper permissions for a resource, and can be categorized under ATT&CK technique T1083 for discovering system information through local files. The exposure of log data may also violate privacy regulations and compliance requirements such as those outlined in ISO 27001 and NIST cybersecurity frameworks.
Mitigation strategies for CVE-2013-0337 involve immediate configuration adjustments to enforce proper file permissions on nginx log files. System administrators should modify the nginx configuration to ensure that log files are created with restrictive permissions, typically using chmod 640 or similar settings that allow only the web server process and authorized administrators to read the files. The recommended approach includes explicitly setting file permissions during log file creation through nginx configuration directives or implementing automated scripts that correct permissions after file creation. Additionally, organizations should conduct regular security audits to verify that log files maintain appropriate access controls and implement monitoring solutions to detect unauthorized access attempts to sensitive system files. The vulnerability can be addressed through proper security hardening practices and adherence to the principle of least privilege as outlined in cybersecurity best practices and industry standards such as those defined by the Center for Internet Security.