CVE-2015-3200 in lighttpd
Summary
by MITRE
mod_auth in lighttpd before 1.4.36 allows remote attackers to inject arbitrary log entries via a basic HTTP authentication string without a colon character, as demonstrated by a string containing a NULL and new line character.
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Analysis
by VulDB Data Team • 05/19/2022
The vulnerability identified as CVE-2015-3200 represents a critical security flaw in the lighttpd web server's authentication module known as mod_auth. This issue affects versions prior to 1.4.36 and exposes the server to remote code execution through log injection attacks. The vulnerability stems from improper input validation within the HTTP basic authentication handling mechanism, where the system fails to properly sanitize authentication strings before processing them for logging purposes.
The technical flaw occurs when a malicious user submits an authentication string that lacks a colon character, which is typically required for basic HTTP authentication. This specific condition allows attackers to inject specially crafted strings containing NULL and newline characters that can manipulate the logging system. The absence of proper sanitization means these control characters can be interpreted by the logging subsystem as actual log entry delimiters or terminators, leading to arbitrary log entry injection. This behavior aligns with CWE-1107, which addresses improper neutralization of special elements used in log entries, and represents a classic case of log injection vulnerability that can be leveraged for various malicious activities.
The operational impact of this vulnerability extends beyond simple log manipulation, as it can enable attackers to craft sophisticated attacks that exploit the logging infrastructure itself. An attacker can manipulate log entries to hide malicious activities, create false log entries, or even inject commands that might be processed by log analysis tools or security monitoring systems. The ability to inject NULL and newline characters creates opportunities for log forging attacks, where the attacker can craft entries that appear legitimate to security tools while actually containing malicious payloads. This vulnerability can be particularly dangerous in environments where security information and event management systems rely on accurate log data for threat detection and incident response.
The attack vector for this vulnerability involves sending specially crafted HTTP requests with authentication strings that bypass normal validation checks. The exploit demonstrates the importance of proper input sanitization and validation in web server components, particularly those involved in authentication and logging operations. Organizations using lighttpd versions prior to 1.4.36 are particularly vulnerable as they cannot properly distinguish between legitimate authentication attempts and maliciously crafted log injection attempts. This vulnerability also connects to ATT&CK technique T1070.002, which covers the use of log injection for evading detection and manipulation of security monitoring systems.
Mitigation strategies for CVE-2015-3200 primarily involve upgrading to lighttpd version 1.4.36 or later, which includes proper input validation and sanitization for authentication strings. Additionally, organizations should implement proper log monitoring and validation procedures to detect anomalous log entries that might indicate injection attempts. Network segmentation and access controls can help limit the impact of successful exploitation, while regular security audits should verify that authentication and logging components are properly configured and validated. The vulnerability serves as a reminder of the critical importance of input validation in security-sensitive components and the potential for seemingly minor flaws to create significant security risks in web server infrastructure.