CVE-2000-0564 in ICQ
Summary
by MITRE
The guestbook CGI program in ICQ Web Front service for ICQ 2000a, 99b, and others allows remote attackers to cause a denial of service via a URL with a long name parameter.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability identified as CVE-2000-0564 resides within the ICQ Web Front service implementation, specifically targeting the guestbook CGI program component that was prevalent in ICQ versions 2000a and 99b. This issue represents a classic denial of service weakness that exploits the service's inadequate input validation mechanisms. The vulnerability manifests when remote attackers craft malicious URLs containing excessively long name parameters, which the guestbook CGI program fails to properly handle. The underlying technical flaw stems from the absence of proper parameter length validation and buffer management within the CGI script, creating a condition where the service becomes unresponsive or crashes upon processing malformed input. This weakness operates at the application layer and demonstrates poor defensive programming practices that were common in early web applications of the late 1990s and early 2000s.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a straightforward method to compromise the availability of ICQ Web Front services. When exploited, the long name parameter causes the CGI program to consume excessive system resources or trigger memory allocation failures, resulting in complete service unavailability for legitimate users. The vulnerability aligns with CWE-122, which addresses buffer overflow conditions, and represents a precursor to more sophisticated denial of service attacks that would later become prevalent in web application security. From an attack framework perspective, this vulnerability maps to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion. The attack vector is particularly concerning because it requires minimal technical expertise to execute and can be performed remotely without authentication, making it an attractive target for malicious actors seeking to disrupt communication services.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and parameter length restrictions within the CGI program. System administrators should configure the service to reject excessively long parameters or implement rate limiting mechanisms to prevent resource exhaustion attacks. The recommended approach involves modifying the guestbook CGI script to validate input parameters against predetermined maximum length limits, typically using server-side validation routines that check parameter lengths before processing. Additionally, deploying web application firewalls and implementing proper error handling can help detect and prevent exploitation attempts. Organizations should also consider upgrading to newer versions of ICQ Web Front services that have addressed this vulnerability through improved input sanitization and buffer management. The remediation process should include comprehensive testing to ensure that legitimate user inputs continue to function while malicious inputs are properly rejected, following security best practices outlined in the OWASP Top Ten and similar industry standards for web application security.