CVE-2009-1160 in PIX
Summary
by MITRE
Cisco Adaptive Security Appliances (ASA) 5500 Series and PIX Security Appliances 7.0 before 7.0(8)1, 7.1 before 7.1(2)74, 7.2 before 7.2(4)9, and 8.0 before 8.0(4)5 do not properly implement the implicit deny statement, which might allow remote attackers to successfully send packets that bypass intended access restrictions, aka Bug ID CSCsq91277.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/01/2019
The vulnerability described in CVE-2009-1160 affects Cisco Adaptive Security Appliances (ASA) 5500 Series and PIX Security Appliances across multiple software versions including 7.0.x, 7.1.x, 7.2.x, and 8.0.x. This represents a critical flaw in the network security device's packet filtering implementation where the implicit deny statement is not properly enforced. The issue stems from the improper handling of access control lists that should automatically deny traffic not explicitly permitted, creating a potential security bypass that could allow unauthorized network access. This vulnerability specifically impacts the core security functionality of these appliances, which are designed to enforce strict network access controls and protect corporate networks from external threats.
The technical flaw manifests in how the security appliances process access control lists and handle packet forwarding decisions. When the implicit deny rule should automatically block packets that do not match any explicit permit statements in the access control list, the implementation fails to properly enforce this security principle. This creates a scenario where packets that should be denied based on the implicit deny rule can successfully traverse the security appliance and reach their intended destinations. The vulnerability affects the fundamental packet filtering mechanism that underpins network security policies, allowing attackers to craft packets that bypass the intended access restrictions. The flaw is particularly concerning because it operates at the core of the appliance's security enforcement capabilities, potentially allowing attackers to gain unauthorized access to protected network segments.
The operational impact of this vulnerability extends beyond simple network access bypass to potentially enable more sophisticated attacks against protected networks. Attackers could exploit this weakness to establish unauthorized communication channels, access restricted resources, or launch further attacks from within the network. The vulnerability affects multiple software versions simultaneously, indicating a systemic issue in the implementation rather than an isolated bug. Organizations using these security appliances could experience unauthorized network access, data breaches, or complete compromise of their network security posture. The impact is particularly severe for enterprises that rely on these appliances for perimeter security, as the vulnerability could allow attackers to bypass all network access controls and gain access to sensitive internal resources.
Organizations should immediately implement mitigations including upgrading to the patched versions of the affected software releases, specifically versions 7.0(8)1, 7.1(2)74, 7.2(4)9, and 8.0(4)5. The vulnerability aligns with CWE-284 Access Control Issues, specifically related to improper access control enforcement in network security appliances. From an attack perspective, this vulnerability maps to ATT&CK techniques involving network penetration and privilege escalation, as attackers can leverage the bypass to gain deeper access to network resources. Additional mitigations include implementing redundant access control measures, monitoring network traffic for suspicious patterns, and conducting thorough network access control reviews. The security community should also consider this vulnerability as an example of how fundamental security principles like implicit deny can be misimplemented in complex network security systems, highlighting the critical importance of proper access control implementation in security appliances.