CVE-2001-0835 in Webalizer
Summary
by MITRE
Cross-site scripting vulnerability in Webalizer 2.01-06, and possibly other versions, allows remote attackers to inject arbitrary HTML tags by specifying them in (1) search keywords embedded in HTTP referrer information, or (2) host names that are retrieved via a reverse DNS lookup.
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Analysis
by VulDB Data Team • 05/10/2019
The vulnerability identified as CVE-2001-0835 represents a critical cross-site scripting flaw in Webalizer version 2.01-06 and potentially other iterations of this web log analysis tool. This security weakness resides in how the application processes and displays user-supplied data within its generated reports, creating an avenue for malicious actors to execute arbitrary HTML code in the context of victims' browsers. The vulnerability specifically manifests when the application incorporates search keywords from HTTP referrer information or host names obtained through reverse DNS lookups without proper input sanitization or output encoding mechanisms.
The technical exploitation of this vulnerability occurs through two primary vectors that leverage the application's handling of untrusted data inputs. First, attackers can manipulate search keywords embedded within HTTP referrer headers by injecting malicious HTML tags directly into the referrer string that the Webalizer application processes and displays in its reports. Second, the vulnerability extends to host name processing where reverse DNS lookups are performed on IP addresses, allowing attackers to control the host name resolution process and inject malicious content through specially crafted host names. Both attack vectors exploit the fundamental principle that user-controllable data should never be directly rendered in web interfaces without proper sanitization, as demonstrated by the weakness mapping to CWE-79 which specifically addresses cross-site scripting vulnerabilities.
The operational impact of this vulnerability extends beyond simple data corruption or display manipulation, as it enables sophisticated attack scenarios that can compromise user sessions and facilitate further exploitation. When a victim views a Webalizer report containing maliciously injected HTML code, the browser executes this code within the context of the victim's session, potentially allowing attackers to steal session cookies, redirect users to malicious sites, or perform actions on behalf of the authenticated user. This threat is particularly concerning because Webalizer reports are typically generated from web server logs and may be accessed by multiple users including administrators, making the attack surface broad and potentially persistent. The vulnerability aligns with ATT&CK technique T1531 which describes the use of malicious content to compromise systems, and represents a classic example of how insecure input handling can create persistent security risks in web applications.
Mitigation strategies for this vulnerability must address both the immediate remediation needs and the underlying architectural weaknesses that enabled the flaw. Organizations should immediately upgrade to a patched version of Webalizer that implements proper input validation and output encoding for all user-supplied data, particularly data retrieved from HTTP referrer headers and DNS resolution results. The implementation of Content Security Policy headers can provide additional defense-in-depth measures to prevent execution of unauthorized scripts even if the primary vulnerability is not fully addressed. Security practitioners should also consider implementing network-level controls to sanitize referrer headers and DNS responses before they reach the Webalizer application, while ensuring that all generated reports undergo proper HTML escaping for any dynamic content. This vulnerability serves as a historical example of why input validation and output encoding should be implemented as fundamental security controls in all web applications, aligning with the OWASP Top Ten security principles that emphasize the importance of preventing injection attacks through proper data sanitization and encoding mechanisms.