CVE-2015-6325 in ASA
Summary
by MITRE
Cisco Adaptive Security Appliance (ASA) software 7.2 and 8.2 before 8.2(5.58), 8.3 and 8.4 before 8.4(7.29), 8.5 through 8.7 before 8.7(1.17), 9.0 before 9.0(4.37), 9.1 before 9.1(6.4), 9.2 before 9.2(4), 9.3 before 9.3(3.1), and 9.4 before 9.4(1.1) allows remote attackers to cause a denial of service (device reload) via a crafted DNS response, aka Bug ID CSCut03495.
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Analysis
by VulDB Data Team • 11/18/2024
The vulnerability identified as CVE-2015-6325 affects Cisco Adaptive Security Appliance (ASA) software across multiple versions including 7.2 and 8.2 through 9.4, presenting a critical remote denial of service flaw that can trigger device reloads through manipulation of DNS responses. This vulnerability resides in the ASA's handling of DNS packets and represents a significant security risk for organizations relying on Cisco ASA firewalls for network protection. The flaw specifically impacts the device's DNS resolver functionality, where improperly crafted DNS responses can cause the appliance to crash and subsequently reload its operating system. The vulnerability is particularly concerning because it allows remote attackers to execute a denial of service attack without requiring authentication or privileged access, making it highly exploitable within the context of network security operations.
The technical implementation of this vulnerability stems from insufficient input validation within the ASA's DNS processing module. When the appliance receives a specially crafted DNS response packet, the system fails to properly validate the packet structure and content before processing it, leading to memory corruption or unexpected behavior in the DNS resolver component. This flaw aligns with CWE-129, which addresses improper validation of input, and CWE-125, which covers out-of-bounds read conditions. The vulnerability can be exploited through a variety of attack vectors including DNS cache poisoning, DNS tunneling, or by manipulating DNS responses through compromised systems within the network or through man-in-the-middle attacks. The attack requires minimal privileges and can be executed from remote locations, making it particularly dangerous for organizations with public-facing ASA appliances.
The operational impact of this vulnerability extends beyond simple service disruption, potentially affecting network availability and business continuity for organizations relying on Cisco ASA appliances for their security infrastructure. When an ASA device reloads due to this vulnerability, it creates a temporary network outage that can affect thousands of users and applications depending on the appliance's role in the network architecture. The vulnerability affects multiple major versions of the ASA software, indicating a widespread exposure across enterprise networks that may have been running these appliances for years without proper patching. This creates a significant risk for organizations that may have delayed security updates due to operational constraints or testing requirements, leaving them vulnerable to exploitation by threat actors who could leverage this weakness to disrupt network services.
Organizations affected by this vulnerability should implement immediate mitigation strategies including applying the relevant Cisco security patches and updates, which address the DNS processing validation issues. Network administrators should also consider implementing DNS filtering mechanisms and monitoring for unusual DNS traffic patterns that might indicate exploitation attempts. The vulnerability can be mitigated through proper patch management procedures and network segmentation to limit the attack surface. From an ATT&CK framework perspective, this vulnerability maps to technique T1499.004, which covers network denial of service attacks, and T1566, which addresses phishing attacks that could be used to deliver the malicious DNS responses. Organizations should also review their incident response procedures to ensure they can quickly detect and respond to device reload events that may indicate exploitation of this vulnerability. The remediation process should include thorough testing of patches in non-production environments before deployment to ensure no unintended side effects occur in the network security infrastructure.