CVE-2015-0676 in ASA
Summary
by MITRE
The DNS implementation in Cisco Adaptive Security Appliance (ASA) Software 7.2 before 7.2(5.16), 8.2 before 8.2(5.57), 8.3 before 8.3(2.44), 8.4 before 8.4(7.28), 8.5 before 8.5(1.24), 8.6 before 8.6(1.17), 8.7 before 8.7(1.16), 9.0 before 9.0(4.33), 9.1 before 9.1(6.1), 9.2 before 9.2(3.4), and 9.3 before 9.3(3) allows man-in-the-middle attackers to cause a denial of service (memory consumption or device outage) by triggering outbound DNS queries and then sending crafted responses to these queries, aka Bug ID CSCuq77655.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 05/02/2022
The vulnerability described in CVE-2015-0676 represents a critical flaw in Cisco Adaptive Security Appliance software that enables man-in-the-middle attackers to execute denial of service attacks against network infrastructure. This vulnerability specifically affects multiple versions of ASA software across several major release lines including 7.2, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 9.0, 9.1, 9.2, and 9.3, making it a widespread issue affecting organizations relying on Cisco security appliances for network protection. The flaw stems from improper handling of DNS responses within the ASA's DNS implementation, creating a pathway for attackers to manipulate the system's memory management and potentially cause complete device outages.
The technical nature of this vulnerability involves the manipulation of outbound DNS queries through crafted responses that exploit memory consumption patterns within the ASA software. When the appliance initiates DNS lookups for various network services, attackers can intercept these queries and respond with malicious DNS records that cause the ASA to consume excessive memory resources or trigger system instability. This particular flaw operates at the network layer and leverages the fundamental DNS protocol mechanics to create a denial of service condition. The vulnerability is classified as a memory exhaustion attack that can lead to complete service disruption, as the ASA's memory management system becomes overwhelmed by the crafted responses. This behavior aligns with CWE-400, which categorizes the vulnerability as a memory allocation issue that can result in resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network availability and security posture. Organizations using affected ASA versions face the risk of complete network outages during attack periods, as the device may become unresponsive or require manual intervention to restore functionality. The attack requires minimal privileges and can be executed from external network positions, making it particularly dangerous for organizations that do not properly segment their network infrastructure. Network administrators may experience extended downtime while troubleshooting the issue, as the symptoms manifest as memory exhaustion rather than clear error conditions. This vulnerability can also impact other network services that depend on the ASA for routing and security functions, potentially creating cascading failures throughout the network infrastructure.
Mitigation strategies for this vulnerability require immediate software updates to patched versions of Cisco ASA software, as outlined in the vendor's security advisories. Organizations should prioritize applying the relevant security patches that address the DNS response handling mechanism and memory consumption issues within the ASA software. Network segmentation and access control measures should be implemented to limit the attack surface, particularly by restricting external access to DNS query mechanisms. Monitoring systems should be enhanced to detect unusual DNS traffic patterns or memory usage spikes that may indicate exploitation attempts. Additionally, organizations should implement proper DNS security measures including DNSSEC validation and consider deploying DNS filtering solutions to prevent unauthorized DNS responses from reaching the ASA appliances. The vulnerability demonstrates the importance of maintaining current security patches and highlights the need for comprehensive network monitoring to detect and respond to exploitation attempts effectively. This issue also aligns with ATT&CK technique T1499, which covers network disruption attacks through resource exhaustion and memory consumption, emphasizing the strategic importance of addressing such vulnerabilities in enterprise security infrastructure.