CVE-1999-1342 in ActiveList Server
Summary
by MITRE
ICQ ActiveList Server allows remote attackers to cause a denial of service (crash) via malformed packets to the server's UDP port.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-1342 represents a classic denial of service flaw affecting the ICQ ActiveList Server implementation. This vulnerability specifically targets the server's handling of UDP traffic on its designated port, creating a condition where malformed packets can trigger system instability and complete service disruption. The issue stems from inadequate input validation mechanisms within the server's network protocol processing layer, allowing attackers to craft specially designed packets that exploit parsing weaknesses in the ActiveList server implementation.
The technical flaw manifests through the server's failure to properly validate incoming UDP packet structures before processing them. When malformed packets are received, the ActiveList server lacks robust error handling and input sanitization routines that would normally prevent malformed data from causing system crashes or unexpected behavior. This vulnerability directly maps to CWE-129, Input Validation, and CWE-20, Improper Input Validation, as the server fails to properly validate the structure and content of incoming network packets. The vulnerability exists at the protocol level where UDP packets are received and parsed without sufficient checks to ensure data integrity and proper formatting.
From an operational perspective, this vulnerability creates significant risk for organizations relying on ICQ ActiveList services as it allows remote attackers to perform unauthorized denial of service attacks. The impact extends beyond simple service disruption to potentially affecting communication infrastructure that depends on ICQ services, particularly in enterprise environments where instant messaging systems form part of critical communication workflows. Attackers can exploit this vulnerability with minimal technical expertise, requiring only basic network packet crafting capabilities to generate the malformed packets that trigger the server crash. This makes the vulnerability particularly dangerous as it can be leveraged by attackers with limited resources to disrupt legitimate service availability.
The attack vector for this vulnerability operates through the UDP protocol, which is connectionless and typically less secure than TCP-based protocols. This characteristic makes it easier for attackers to send malformed packets without establishing proper connections or maintaining session state, allowing for rapid and effective denial of service attacks. The vulnerability's exploitation aligns with ATT&CK technique T1498, Network Denial of Service, as it specifically targets network availability by causing service disruption through malformed packet delivery. Organizations should consider implementing network segmentation and access control measures to limit exposure to such vulnerabilities, particularly in environments where ICQ services are actively used.
Mitigation strategies for CVE-1999-1342 should include immediate patching of affected systems, implementing network filtering rules to block suspicious UDP traffic, and deploying intrusion detection systems that can identify malformed packet patterns. Network administrators should also consider disabling unnecessary UDP services and ports that are not essential to business operations. The vulnerability highlights the importance of robust input validation in network services and demonstrates how seemingly minor implementation flaws can result in significant operational impact. Security monitoring should include detection of unusual UDP traffic patterns and packet structures that may indicate exploitation attempts, while system administrators should maintain comprehensive logging of network service behavior to identify potential exploitation attempts.