CVE-2002-2103 in HTTP Server
Summary
by MITRE
Apache before 1.3.24, when writing to the log file, records a spoofed hostname from the reverse lookup of an IP address, even when a double-reverse lookup fails, which allows remote attackers to hide the original source of activities.
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Analysis
by VulDB Data Team • 08/30/2025
The vulnerability described in CVE-2002-2103 affects Apache HTTP Server versions prior to 1.3.24 and represents a significant logging security flaw that impacts the integrity of audit trails. This issue stems from the server's handling of hostname resolution during log file creation, where the software attempts to perform reverse DNS lookups to associate IP addresses with hostnames for logging purposes. The vulnerability becomes particularly concerning when double-reverse lookup procedures fail, as the system continues to record potentially spoofed hostname information rather than properly handling the failed resolution attempt.
The technical flaw in this vulnerability resides in the Apache server's logging mechanism that fails to properly validate reverse DNS lookup results. When a client connects to the web server, Apache attempts to resolve the client's IP address to a hostname through reverse DNS lookup. In normal circumstances, this process works correctly, but when the reverse lookup fails, the system should either abandon the hostname logging or use a default value indicating the lookup failure. However, Apache before version 1.3.24 continues to record what appears to be a hostname from a failed double-reverse lookup, creating misleading log entries that can be exploited by malicious actors.
This vulnerability creates substantial operational impact by enabling attackers to obfuscate their true source IP addresses and potentially mask their activities from security monitoring systems. The ability to hide the original source of network activities means that security analysts and administrators cannot accurately trace the origin of attacks or suspicious behavior through log analysis. This effectively undermines the fundamental purpose of web server logging as a security control, as the log entries become unreliable indicators of actual client behavior. The spoofed hostname information can be manipulated to appear as if requests are coming from legitimate systems or locations, making it extremely difficult to perform effective threat hunting or incident response activities.
The vulnerability aligns with CWE-693, which addresses protection mechanisms that are insufficient or ineffective, and can be categorized under ATT&CK technique T1562.001, which involves disabling or circumventing security tools. Attackers can exploit this weakness to conduct reconnaissance, perform malicious activities, and evade detection by creating false audit trails. Organizations that rely on web server logs for security monitoring, compliance reporting, or forensic analysis face significant risks when this vulnerability exists in their infrastructure. The flaw essentially allows attackers to manipulate the very data that should serve as evidence of their activities, making it a critical security concern for any environment where Apache web servers are deployed without proper patching.
The recommended mitigation strategy involves upgrading to Apache HTTP Server version 1.3.24 or later, which contains the necessary fixes to properly handle failed reverse DNS lookups. Additionally, system administrators should implement proper log validation procedures and consider configuring Apache to disable reverse DNS lookups entirely if hostname resolution is not critical for their operations. Organizations should also establish monitoring procedures to detect anomalous logging patterns that might indicate exploitation attempts. The fix implemented in Apache 1.3.24 addresses the core issue by ensuring that failed reverse lookups do not result in spoofed hostname entries, thereby maintaining the integrity of audit logs and preserving the ability to accurately trace network activities back to their true sources.