A vulnerability in the DNS Application Layer Protocol Inspection (ALPI) engine of Cisco ASA Software could allow an unauthenticated, remote attacker to trigger a reload of the affected device.
The vulnerability is due to improper processing of unsupported DNS over TCP packets by the DNS inspection engine. An attacker could exploit this vulnerability by sending crafted DNS messages over TCP through an affected device.
Cisco has confirmed the vulnerability in a security advisory and released software updates.
Indicators of Compromise
Cisco Adaptive Security Appliance Software versions prior to 8.2(5.46), 8.3(2.39), 8.4(7), 8.5(1.18), 8.6(1.12), 8.7(1.7), 9.0(3.2), and 9.1(1.8) are vulnerable.
The vulnerability is due to improper processing of DNS packets by the DNS ALPI engine in Cisco Adaptive Security Appliance Software.
An unauthenticated, remote attacker could exploit the vulnerability by sending malicious DNS packets over TCP that are designed to transit a vulnerable device. The processing of the malicious packets could cause the device to reload, resulting in a DoS condition.
Only devices with DNS ALPI enabled are vulnerable, reducing the potential for exploitation.
Administrators are advised to apply the appropriate updates.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators are advised to monitor affected systems.
Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via email at email@example.com.
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.