CVE-2016-6431 in ASA
Summary
by MITRE
A vulnerability in the local Certificate Authority (CA) feature of Cisco ASA Software before 9.6(1.5) could allow an unauthenticated, remote attacker to cause a reload of the affected system. The vulnerability is due to improper handling of crafted packets during the enrollment operation. An attacker could exploit this vulnerability by sending a crafted enrollment request to the affected system. An exploit could allow the attacker to cause the reload of the affected system. Note: Only HTTPS packets directed to the Cisco ASA interface, where the local CA is allowing user enrollment, can be used to trigger this vulnerability. This vulnerability affects systems configured in routed firewall mode and in single or multiple context mode.
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Analysis
by VulDB Data Team • 09/24/2024
The vulnerability described in CVE-2016-6431 represents a critical denial-of-service flaw within Cisco Adaptive Security Appliance (ASA) software versions prior to 9.6(1.5). This weakness specifically targets the local Certificate Authority feature, which is designed to enable certificate enrollment operations within the firewall environment. The vulnerability stems from inadequate validation of incoming enrollment requests, creating an exploitable condition that can be leveraged by remote attackers without requiring authentication credentials. The flaw manifests when the system processes malformed packets during the certificate enrollment process, leading to a system reload that effectively disrupts network security operations.
The technical implementation of this vulnerability involves the improper handling of crafted packets that are specifically designed to trigger buffer overflows or memory corruption conditions within the certificate enrollment module. Attackers can exploit this weakness by sending specially constructed enrollment requests through HTTPS traffic directed to the ASA interface where local CA functionality is enabled. The attack vector requires that the target system be configured in routed firewall mode or single/multiple context mode, with the local CA feature actively allowing user enrollment operations. This constraint limits the attack surface but does not eliminate the severity of the vulnerability, as it can still affect organizations with properly configured ASA deployments.
From an operational impact perspective, this vulnerability poses significant risks to network availability and security infrastructure reliability. The ability to remotely force a system reload without authentication creates a substantial threat to business continuity, as it can be used to disrupt critical network security services. The exploitability of this vulnerability means that attackers can potentially cause repeated disruptions, leading to service degradation or complete network outages depending on the frequency and timing of attacks. Organizations relying on Cisco ASA appliances for security enforcement may experience unauthorized service interruptions that could compromise their overall security posture.
The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and demonstrates characteristics consistent with improper input validation flaws. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1499.004, which covers network denial of service attacks through system reload or restart operations. The lack of authentication requirements makes this particularly dangerous as it allows for exploitation from any remote location without the need for prior access credentials. Organizations should consider implementing network segmentation and access controls to limit exposure, while also ensuring that all ASA deployments are updated to versions that address this specific vulnerability. The remediation process requires careful planning to avoid service disruption during the patching process, particularly in mission-critical environments where continuous availability is essential.