CVE-2003-1580 in HTTP Server
Summary
by MITRE
The Apache HTTP Server 2.0.44, when DNS resolution is enabled for client IP addresses, uses a logging format that does not identify whether a dotted quad represents an unresolved IP address, which allows remote attackers to spoof IP addresses via crafted DNS responses containing numerical top-level domains, as demonstrated by a forged 123.123.123.123 domain name, related to an "Inverse Lookup Log Corruption (ILLC)" issue.
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Analysis
by VulDB Data Team • 04/30/2026
The vulnerability described in CVE-2003-1580 represents a critical flaw in the Apache HTTP Server 2.0.44 implementation of DNS resolution logging mechanisms. This issue specifically manifests when the server operates with DNS resolution enabled for client IP addresses, a common configuration in web server deployments where administrators require detailed logging of client hostnames rather than just IP addresses. The fundamental problem lies in how the server handles the logging of resolved IP addresses, particularly when DNS resolution fails or produces unexpected results.
The technical flaw stems from the server's inability to distinguish between properly resolved IP addresses and those that have been resolved through malformed or forged DNS responses. When DNS resolution is enabled, Apache attempts to perform reverse DNS lookups on client IP addresses to obtain hostname information for logging purposes. However, the logging format used by the server does not include explicit indicators to differentiate between successfully resolved addresses and those that have been spoofed through malicious DNS responses. This creates a scenario where forged DNS responses containing numerical top-level domains can be interpreted as valid hostnames.
The operational impact of this vulnerability is significant and directly relates to the concept of log integrity and audit trail corruption. Attackers can exploit this weakness by crafting malicious DNS responses that contain numerical domain names such as the demonstrated example of 123.123.123.123, which would be interpreted by the server as a valid hostname rather than a numerical IP address. This spoofing capability allows malicious actors to manipulate web server logs, potentially obscuring their true IP addresses and making it difficult for security analysts to track and identify actual attackers. The vulnerability essentially creates a false narrative in server logs, where legitimate-looking hostnames are generated from forged DNS responses.
This vulnerability maps directly to CWE-200, which deals with the exposure of sensitive information, and specifically addresses issues related to information leakage through improper logging mechanisms. The flaw also aligns with ATT&CK technique T1562.001, which covers "TTP: Impair Defenses - Disable or Modify Tools," as it allows attackers to evade detection by corrupting log data that would normally be used for monitoring and forensic analysis. The issue represents a form of log manipulation that can be used to cover tracks and bypass security controls that rely on accurate IP address information for threat detection.
The root cause of this vulnerability lies in the lack of proper validation and sanitization of DNS resolution results before logging them in the server's access logs. When the Apache server performs reverse DNS lookups, it does not validate that the resulting hostname actually corresponds to the original IP address, nor does it implement any mechanism to detect or flag potentially forged DNS responses. This oversight creates an attack surface where DNS-based spoofing can be leveraged to manipulate the server's logging behavior and compromise the integrity of the audit trail. Organizations using Apache 2.0.44 with DNS resolution enabled are particularly vulnerable to this attack vector, as the flaw exists in the core logging functionality of the web server.
Mitigation strategies for this vulnerability involve multiple approaches that address both the immediate security concern and the underlying architectural issues. The most effective immediate solution is to disable DNS resolution for client IP addresses in the Apache configuration when it is not strictly necessary for application functionality. This can be achieved by setting the UseCanonicalName directive appropriately and ensuring that the server does not perform reverse DNS lookups in the logging process. Additionally, implementing proper DNS validation mechanisms and monitoring for unusual DNS resolution patterns can help detect potential exploitation attempts. Organizations should also consider upgrading to newer versions of Apache HTTP Server where this vulnerability has been addressed through improved logging mechanisms and better validation of DNS resolution results. The fix typically involves enhanced logging formats that explicitly indicate when DNS resolution has failed or when results may be unreliable, thereby preventing the corruption of audit trails through forged DNS responses.