CVE-2009-2801 in Mac OS X
Summary
by MITRE
The Application Firewall in Apple Mac OS X 10.5.8 drops unspecified firewall rules after a reboot, which might allow remote attackers to bypass intended access restrictions via packet data, related to a "timing issue."
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Analysis
by VulDB Data Team • 05/03/2026
The vulnerability described in CVE-2009-2801 represents a critical flaw in Apple Mac OS X 10.5.8's Application Firewall implementation that creates a window of opportunity for remote attackers to circumvent network access controls. This timing-based vulnerability specifically affects the firewall's ability to maintain its rule set across system reboots, creating a temporary security gap where the firewall operates with reduced or default configurations. The issue stems from the improper handling of firewall rules during the system boot process, where unspecified or unprocessed rules are inadvertently discarded rather than properly initialized, leaving the system temporarily exposed to unauthorized network access attempts. This flaw directly impacts the integrity of the firewall's security posture and represents a fundamental failure in the rule persistence mechanism that should ensure consistent network protection throughout system operations.
The technical implementation of this vulnerability involves a race condition or timing issue within the firewall initialization sequence that occurs during system reboot processes. When Mac OS X 10.5.8 restarts, the Application Firewall service undergoes a restart sequence that fails to properly maintain or reapply all previously configured rules. The system's firewall management subsystem appears to drop or ignore certain firewall rules that were active before the reboot, particularly those that are not explicitly defined or are considered unspecified within the rule set. This behavior creates a temporal window where the firewall operates in a default state or with minimal restrictions, allowing remote attackers to exploit this gap by sending specially crafted packet data that would normally be blocked by the full rule set. The timing aspect of this vulnerability means that the window of exposure occurs immediately after reboot and before the firewall has fully re-established its complete rule configuration.
The operational impact of this vulnerability extends beyond simple network access control breaches, as it fundamentally undermines the trust model that users place in their firewall protection mechanisms. During the brief period following system reboot, attackers can potentially establish unauthorized connections, conduct reconnaissance activities, or exploit services that should normally be restricted. This vulnerability is particularly dangerous because it operates silently without generating obvious alerts or logs, making detection difficult for security monitoring systems. The timing issue creates a scenario where network traffic that should be filtered or blocked by the firewall passes through unimpeded, potentially allowing attackers to establish persistent connections, exfiltrate data, or conduct further exploitation activities. The vulnerability's impact is amplified because it affects the core network protection mechanism that users expect to function consistently across all system states, including reboot scenarios.
Mitigation strategies for this vulnerability require immediate system updates and configuration adjustments to address the timing issue in firewall rule persistence. Apple's recommended solution involves applying the latest security patches and updates that specifically address the firewall initialization sequence and rule persistence mechanisms. Organizations should implement additional monitoring controls to detect unusual network traffic patterns that might indicate exploitation attempts during system reboot windows. The implementation of network segmentation and additional layers of security controls can help minimize the impact if this vulnerability is exploited. Security administrators should also consider implementing automated systems that can verify firewall rule configurations immediately after system reboots and alert on any inconsistencies. From a compliance perspective, this vulnerability relates to CWE-362 which addresses race conditions in security-critical operations, and may be mapped to ATT&CK technique T1072 which involves software deployment methods that can be exploited to bypass security controls. Organizations should conduct regular audits of their firewall configurations and establish procedures for validating network protection mechanisms after any system restart or update activities.