CVE-2002-0180 in Webalizer
Summary
by MITRE
Buffer overflow in Webalizer 2.01-06, when configured to use reverse DNS lookups, allows remote attackers to execute arbitrary code by connecting to the monitored web server from an IP address that resolves to a long hostname.
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Analysis
by VulDB Data Team • 09/22/2025
The vulnerability described in CVE-2002-0180 represents a critical buffer overflow flaw in Webalizer version 2.01-06 that specifically manifests when the application is configured to perform reverse DNS lookups. This security weakness stems from inadequate input validation and memory management within the web log analysis tool that processes incoming connection data from monitored web servers. The flaw occurs because Webalizer fails to properly constrain the length of hostname strings obtained through reverse DNS resolution, creating an exploitable condition where attacker-controlled data can overflow fixed-length buffers in memory.
The technical implementation of this vulnerability leverages the standard DNS resolution process to create a malicious attack vector. When Webalizer processes incoming web server connections and performs reverse DNS lookups to determine hostnames, it assumes that hostname resolution will produce reasonably sized output. However, when an attacker controls the source IP address that resolves to an extremely long hostname through DNS manipulation, the application attempts to store this oversized string in a pre-allocated buffer that cannot accommodate the excessive data length. This buffer overflow condition creates opportunities for arbitrary code execution, as the overflow can overwrite adjacent memory locations including return addresses and control structures within the program's execution flow.
The operational impact of this vulnerability extends beyond simple remote code execution, as it provides attackers with potential persistence mechanisms and privilege escalation opportunities within the system where Webalizer is deployed. Attackers can exploit this weakness to gain unauthorized access to web server monitoring systems, potentially compromising the integrity of log analysis data and gaining access to sensitive operational information. The vulnerability affects systems where Webalizer is configured with reverse DNS lookup functionality enabled, which was a common configuration in web server monitoring environments during the early 2000s. This flaw aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of insufficient bounds checking in input handling processes.
Mitigation strategies for CVE-2002-0180 should focus on immediate patch application and configuration hardening measures. System administrators should upgrade to Webalizer versions that address this buffer overflow vulnerability, as the original 2.01-06 release contained no built-in protections against oversized hostname inputs. Additionally, organizations should disable reverse DNS lookup functionality within Webalizer when it is not essential for their monitoring requirements, as this configuration option directly enables the exploit path. Network-level controls such as DNS query filtering and monitoring for unusually long hostname resolutions can provide additional defensive layers. From an ATT&CK framework perspective, this vulnerability maps to techniques involving remote code execution and privilege escalation through software vulnerabilities, with the attack surface expanding to include web server monitoring infrastructure and log analysis systems that rely on DNS resolution for host identification. The vulnerability demonstrates the importance of input validation in security-critical applications and highlights how seemingly benign features like reverse DNS lookups can create dangerous attack vectors when not properly constrained.