CVE-2000-0792 in Gnome-Lokkit
Summary
by MITRE
Gnome Lokkit firewall package before 0.41 does not properly restrict access to some ports, even if a user does not make any services available.
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Analysis
by VulDB Data Team • 05/27/2018
The vulnerability identified as CVE-2000-0792 resides within the Gnome Lokkit firewall package version 0.40 and earlier, representing a significant security flaw in network access control mechanisms. This issue affects systems utilizing the Gnome desktop environment where Lokkit serves as a graphical interface for configuring firewall settings. The flaw manifests when users configure their firewall through the Lokkit interface without explicitly making any services available, yet the system still permits access to certain ports that should remain restricted. This represents a classic case of improper access control where the firewall fails to properly enforce its security policies even in the absence of explicit service exposure.
The technical root cause of this vulnerability stems from the package's failure to implement proper port restriction mechanisms within its firewall configuration logic. When users interact with Lokkit's graphical interface, they expect that disabling services or leaving configuration fields blank would result in complete port blocking for those services. However, the implementation contains a logic flaw that allows certain network ports to remain accessible despite the user's intention to restrict access. This misconfiguration occurs at the kernel level where firewall rules are applied, specifically in how the package translates user interface selections into actual iptables or similar firewall rule sets. The vulnerability operates under CWE-284, which classifies improper access control, and demonstrates how graphical user interfaces can mask underlying security implementation flaws.
The operational impact of this vulnerability extends beyond simple network exposure, as it creates potential attack vectors that adversaries can exploit to gain unauthorized access to systems. Attackers could leverage the unrestricted ports to conduct reconnaissance, establish reverse shells, or perform other malicious activities without the system owner's knowledge or consent. This vulnerability is particularly dangerous because it operates silently in the background, with users believing their systems are properly secured while remaining vulnerable to network-based attacks. The flaw persists even when users follow standard security practices by not exposing services, making it a particularly insidious issue that undermines the fundamental security assumptions of firewall configuration. This vulnerability directly aligns with ATT&CK technique T1046, which involves network service scanning and access to network services, as the restricted ports essentially provide unauthorized access paths to networked systems.
The mitigation strategy for this vulnerability requires immediate upgrading to Lokkit version 0.41 or later, which contains the necessary patches to properly enforce port restrictions. System administrators should conduct comprehensive audits of their firewall configurations to ensure that no unauthorized ports remain accessible, particularly focusing on the specific port ranges that were affected by this vulnerability. Additionally, organizations should implement continuous monitoring of firewall rule sets to detect any anomalies that might indicate similar access control flaws. The fix implemented in version 0.41 addresses the core logic error by ensuring that when no services are explicitly configured to be available, all associated ports are properly restricted. Security teams should also consider implementing network segmentation and additional access controls beyond the firewall to provide defense in depth. This vulnerability underscores the importance of thorough testing of security configurations and the necessity of validating that user interface selections translate correctly into effective security policies. The incident highlights how seemingly minor implementation flaws in security tools can create significant vulnerabilities that compromise entire network infrastructures.