CVE-2002-2266 in ScreenOS
Summary
by MITRE
NetScreen ScreenOS 2.8 through 4.0, when forwarding H.323 or Netmeeting traffic, allows remote attackers to cause a denial of service (firewall session table consumption) by establishing multiple half-open H.323 sessions, which are not cleaned up on garbage removal and do not time out for 36 hours.
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Analysis
by VulDB Data Team • 03/25/2017
The vulnerability described in CVE-2002-2266 represents a significant denial of service weakness in NetScreen ScreenOS firewall implementations ranging from version 2.8 through 4.0. This flaw specifically targets the handling of H.323 and Netmeeting traffic, which are protocols commonly used for voice and video communication over IP networks. The issue manifests when the firewall forwards these types of traffic, creating a scenario where remote attackers can exploit the system's session management capabilities to consume available resources. The vulnerability operates through a specific mechanism involving the creation of multiple half-open H.323 sessions that persist in the firewall's session table despite normal cleanup processes. This behavior directly relates to CWE-400, which addresses improper handling of resource exhaustion conditions in software systems.
The technical implementation of this vulnerability stems from the firewall's failure to properly manage session cleanup for H.323 protocols. When half-open sessions are established, they remain in the active session table indefinitely until explicitly terminated, with no automatic timeout mechanism for these specific protocol types. The 36-hour timeout period represents a critical design flaw that allows attackers to maintain these sessions for extended periods without system intervention. This particular implementation issue affects the firewall's resource management capabilities and demonstrates a lack of proper session lifecycle management for multimedia protocols. The vulnerability operates at the network protocol level and specifically impacts the session table management functions within the ScreenOS operating system, which is a proprietary firewall operating system developed by Juniper Networks.
The operational impact of this vulnerability extends beyond simple service disruption to create a persistent resource exhaustion condition that can severely degrade firewall performance. Attackers can maintain numerous half-open sessions simultaneously, causing the session table to fill rapidly and eventually leading to complete denial of service for legitimate traffic. This condition affects the firewall's ability to process new connections and can result in complete network connectivity issues for users attempting to establish legitimate H.323 or Netmeeting sessions. The long timeout period of 36 hours allows for sustained attacks that can persist for extended periods without requiring additional exploitation attempts. The vulnerability particularly impacts enterprise networks that rely on H.323 for voice communication services, as it can effectively shut down critical communication infrastructure.
Mitigation strategies for CVE-2002-2266 should focus on both immediate operational fixes and long-term architectural improvements to firewall session management. Immediate remediation includes implementing session timeout mechanisms for H.323 traffic that override the default 36-hour timeout, configuring rate limiting for incoming H.323 connections, and establishing monitoring procedures to detect unusual session table growth. Network administrators should also consider implementing access control lists that restrict H.323 traffic to trusted sources only, thereby reducing the attack surface. The vulnerability aligns with ATT&CK technique T1499 which covers network denial of service attacks, and represents a classic example of resource exhaustion attacks that can be mitigated through proper session management and monitoring. Organizations should also consider upgrading to newer versions of ScreenOS that address these session management deficiencies, as the vulnerability was resolved in subsequent releases of the firewall operating system. The implementation of these mitigations should be part of broader network security monitoring and incident response procedures to ensure rapid detection and remediation of similar vulnerabilities.