CVE-2000-0339 in ZoneAlarm
Summary
by MITRE
ZoneAlarm 2.1.10 and earlier does not filter UDP packets with a source port of 67, which allows remote attackers to bypass the firewall rules.
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Analysis
by VulDB Data Team • 06/15/2025
The vulnerability described in CVE-2000-0339 represents a significant firewall bypass flaw in ZoneAlarm version 2.1.10 and earlier releases. This issue stems from the software's inadequate handling of specific UDP packet headers, particularly those originating from port 67, which is the standard port used by the Dynamic Host Configuration Protocol for bootstrapping network settings. The flaw exists at the packet filtering layer where the firewall fails to properly validate source port information, creating an exploitable condition that undermines the security posture of systems relying on ZoneAlarm for network protection.
The technical implementation of this vulnerability occurs at the network packet inspection level where ZoneAlarm's firewall rules do not adequately filter incoming UDP packets based on source port 67. This particular port is reserved for DHCP servers to respond to client requests, and the firewall should normally enforce strict rules to prevent unauthorized access. However, the flaw allows attackers to craft malicious packets that appear to originate from legitimate DHCP server traffic, effectively bypassing the firewall's intended security controls. This represents a classic case of insufficient input validation and protocol handling where the software fails to properly distinguish between legitimate and malicious traffic patterns.
The operational impact of this vulnerability extends beyond simple firewall bypass to potentially enable a range of malicious activities including man-in-the-middle attacks, network reconnaissance, and unauthorized access to network resources. Attackers can exploit this weakness to inject malicious packets into networks, potentially disrupting DHCP services or gaining unauthorized access to systems that rely on proper DHCP functionality for network configuration. The vulnerability affects systems where ZoneAlarm is actively running as a firewall, making it particularly dangerous in corporate environments where network security is paramount. This flaw essentially provides a backdoor mechanism that allows attackers to circumvent network protection without requiring additional privileges or sophisticated attack vectors.
Security professionals should note that this vulnerability aligns with CWE-284, which addresses insufficient access control, and represents a failure in proper privilege and access control mechanisms. The flaw also connects to ATT&CK technique T1071.004 for application layer protocol: DNS, since it involves manipulation of network protocols that can be leveraged for broader attack surface expansion. Organizations should implement immediate mitigations including updating to ZoneAlarm versions that properly address this filtering issue, implementing additional network segmentation measures, and deploying network monitoring tools to detect anomalous traffic patterns that might indicate exploitation attempts. The vulnerability underscores the critical importance of proper packet filtering implementations and highlights the need for comprehensive security testing of firewall and network protection software to prevent such bypass mechanisms from being exploited in real-world scenarios.