CVE-2005-2019 in FreeBSD
Summary
by MITRE
ipfw in FreeBSD 5.4, when running on Symmetric Multi-Processor (SMP) or Uni Processor (UP) systems with the PREEMPTION kernel option enabled, does not sufficiently lock certain resources while performing table lookups, which can cause the cache results to be corrupted during multiple concurrent lookups, allowing remote attackers to bypass intended access restrictions.
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Analysis
by VulDB Data Team • 06/06/2019
The vulnerability identified as CVE-2005-2019 represents a critical race condition within the ipfw packet filtering framework of FreeBSD 5.4 systems. This flaw specifically manifests when the operating system is configured with either Symmetric Multi-Processor or Uni Processor architectures and includes the PREEMPTION kernel option. The core issue stems from inadequate synchronization mechanisms during table lookup operations, creating a scenario where concurrent access to shared resources can result in corrupted cache data structures. The vulnerability operates at the kernel level and directly impacts the integrity of the firewall's access control mechanisms, potentially allowing unauthorized network access that should have been prevented by the configured rules.
The technical implementation of this vulnerability involves the ipfw subsystem's failure to properly implement locking mechanisms during concurrent table lookups. When multiple processes or threads attempt to access the same firewall table simultaneously, the absence of proper mutex or spinlock protection allows race conditions to occur. This concurrency issue is particularly dangerous because it affects the fundamental caching behavior of the packet filtering system, where lookup results become corrupted and inconsistent. The corrupted cache data can cause the firewall to make incorrect routing decisions or fail to properly enforce access control policies, creating potential attack vectors for remote adversaries.
From an operational perspective, this vulnerability presents a significant security risk as it allows remote attackers to bypass access restrictions that should be enforced by the ipfw firewall. The impact extends beyond simple packet filtering failures to potentially enable unauthorized network access, data exfiltration, or service disruption. Attackers could exploit this flaw to circumvent firewall rules, gain access to restricted network segments, or perform other malicious activities that would normally be blocked by properly functioning access control lists. The vulnerability's presence in the kernel space makes it particularly dangerous as it operates below the level of normal user-space security controls and can affect the entire system's network security posture.
The vulnerability maps directly to CWE-362, which describes a race condition in concurrent programming where multiple threads or processes access shared resources without proper synchronization. This aligns with the ATT&CK framework's T1562.007 technique for "Hide Artifacts" and T1071.004 for "Application Layer Protocol: DNS" as attackers could potentially use this vulnerability to bypass network controls and establish covert communication channels. Organizations running FreeBSD 5.4 systems with ipfw and preemption enabled should immediately implement mitigations including disabling the preemption kernel option, applying the appropriate security patches, or upgrading to newer stable FreeBSD releases that have addressed this concurrency issue. Additionally, network segmentation and redundant access control measures should be implemented as defensive controls to limit the potential impact of this vulnerability.