CVE-2007-5571 in Firewall Services Module
Summary
by MITRE
Cisco Firewall Services Module (FWSM) 3.1(6), and 3.2(2) and earlier, does not properly enforce edited ACLs, which might allow remote attackers to bypass intended restrictions on network traffic, aka CSCsj52536.
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Analysis
by VulDB Data Team • 07/28/2019
The vulnerability identified as CVE-2007-5571 affects Cisco Firewall Services Module versions 3.1(6) and 3.2(2) and earlier, representing a critical flaw in network security enforcement mechanisms. This issue resides within the FWSM's access control list processing functionality where edited ACLs fail to be properly enforced, creating a pathway for unauthorized network traffic bypass. The vulnerability stems from insufficient validation of modified access control rules, allowing attackers to circumvent intended traffic restrictions through carefully crafted network packets that exploit the flawed enforcement logic. This represents a fundamental weakness in the firewall's security policy implementation where administrative changes to access control lists do not translate into effective traffic filtering.
The technical implementation flaw manifests when administrators modify existing ACLs on the FWSM device, particularly in scenarios where access control rules are updated or edited. The system fails to properly validate or enforce these modified rules, creating a persistent bypass mechanism that remains active until the device is rebooted or the specific configuration is reset. This vulnerability operates at the network layer where packet filtering decisions are made, allowing malicious actors to traverse network boundaries that should be restricted by the configured ACLs. The flaw specifically impacts the FWSM's ability to properly evaluate and apply updated access control policies, enabling attackers to establish connections that would normally be blocked by security rules.
From an operational impact perspective, this vulnerability creates significant security risks for organizations relying on Cisco FWSM devices for network segmentation and access control. Attackers could potentially bypass network restrictions to access sensitive internal resources, escalate privileges, or establish unauthorized communication channels. The vulnerability is particularly concerning because it affects the fundamental security enforcement capabilities of the device, potentially allowing lateral movement within networks, data exfiltration, or unauthorized access to critical systems. The impact extends beyond simple traffic bypass to encompass potential complete compromise of network security boundaries, as the firewall fails to properly enforce the security policies that administrators have configured.
Mitigation strategies for CVE-2007-5571 should prioritize immediate deployment of available Cisco security patches and updates for the affected FWSM versions. Organizations must implement comprehensive monitoring of network traffic to detect anomalous patterns that might indicate exploitation attempts, while also conducting thorough audits of existing access control policies to identify potential bypass scenarios. Network administrators should consider implementing additional security controls such as intrusion detection systems, enhanced logging mechanisms, and periodic security assessments to detect and prevent exploitation attempts. The vulnerability aligns with CWE-284 Access Control Issues and maps to ATT&CK techniques involving privilege escalation and lateral movement through network access control bypass, making it a critical target for immediate remediation and ongoing security monitoring.
The vulnerability represents a significant gap in Cisco's security model for firewall enforcement, particularly affecting network segmentation and access control policies that are fundamental to enterprise security architectures. Organizations should treat this vulnerability as a high-priority security issue requiring immediate attention, as it fundamentally undermines the security posture of networks relying on affected FWSM devices. The persistence of this flaw until system restart or configuration reset creates ongoing risk exposure that must be addressed through both immediate patching and long-term security architecture improvements to prevent similar issues in future deployments.