CVE-2001-0589 in Netscreen ScreenOS
Summary
by MITRE
NetScreen ScreenOS prior to 2.5r6 on the NetScreen-10 and Netscreen-100 can allow a local attacker to bypass the DMZ denial policy via specific traffic patterns.
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Analysis
by VulDB Data Team • 04/08/2019
The vulnerability identified as CVE-2001-0589 represents a critical security flaw in NetScreen ScreenOS versions prior to 2.5r6 affecting NetScreen-10 and NetScreen-100 devices. This issue specifically targets the firewall's handling of traffic patterns that traverse the demilitarized zone, creating a potential pathway for local attackers to circumvent established security policies. The flaw resides in the operating system's packet processing logic where certain traffic sequences are not properly evaluated against the configured DMZ denial rules, allowing unauthorized access to protected network segments.
The technical implementation of this vulnerability stems from improper state tracking within the firewall's packet inspection engine. When specific traffic patterns are transmitted through the device, the ScreenOS fails to maintain consistent policy evaluation across all traffic flows, particularly in scenarios involving established connections and subsequent packets. This misconfiguration allows attackers to exploit timing variations and packet sequencing to bypass the DMZ denial policy that should normally prevent direct access to internal network resources from external interfaces. The vulnerability operates at the network layer where the firewall's stateful inspection mechanism becomes inconsistent in its application of access control policies.
From an operational impact perspective, this vulnerability creates significant risk for organizations relying on NetScreen firewalls for perimeter security. Local attackers who have gained access to the device can exploit this weakness to gain unauthorized access to systems within the DMZ or internal networks that should remain protected from external threats. The implications extend beyond simple access bypass, as this flaw could potentially enable further escalation attacks where attackers use the compromised firewall as a stepping stone to infiltrate deeper network segments. The vulnerability affects organizations that have not yet upgraded to ScreenOS 2.5r6, leaving their network infrastructure exposed to potential exploitation.
The flaw aligns with CWE-284, which addresses improper access control in network security implementations, and demonstrates how inadequate state management can create security holes in firewall systems. From an attack perspective, this vulnerability maps to ATT&CK technique T1046, which involves network service scanning and reconnaissance activities that can be leveraged to identify and exploit weak points in firewall configurations. Organizations should prioritize immediate patching of affected devices to address this vulnerability, as the window for exploitation remains open for systems running outdated ScreenOS versions. Additional mitigations should include network segmentation, monitoring for unusual traffic patterns, and implementing additional layers of access control to reduce the impact if exploitation occurs. The vulnerability underscores the importance of maintaining current security patches and the critical role that proper stateful inspection plays in network security implementations.