CVE-2020-2031: 
PAN-OS vulnerability analysis and mitigation

CVE-2020-2031 is an integer underflow vulnerability discovered in the dnsproxyd component of the PAN-OS management interface. The vulnerability was discovered internally by Jin Chen of Palo Alto Networks and was disclosed on July 8, 2020. This issue specifically impacts PAN-OS 9.1 versions earlier than PAN-OS 9.1.3, while PAN-OS 8.1, PAN-OS 9.0, and Prisma Access services are not affected (Palo Alto Advisory).

The vulnerability is classified as an integer underflow (CWE-191) in the dnsproxyd component of the PAN-OS management interface. It received a CVSSv3.1 Base Score of 4.9 (MEDIUM), with the following metrics: Attack Vector: NETWORK, Attack Complexity: LOW, Privileges Required: HIGH, User Interaction: NONE, Scope: UNCHANGED, Confidentiality Impact: NONE, Integrity Impact: NONE, Availability Impact: HIGH (Palo Alto Advisory).

When exploited, this vulnerability allows authenticated administrators to issue a command from the command line interface that causes the dnsproxyd component to stop responding. Repeated attempts to send this request result in denial of service to all PAN-OS services by restarting the device and putting it into maintenance mode (Palo Alto Advisory).

The vulnerability requires network access and high privileges (authenticated administrator access) to exploit, though it has a low attack complexity. The attack does not require user interaction to execute (Palo Alto Advisory).

The vulnerability has been fixed in PAN-OS 9.1.3 and all later PAN-OS versions. For systems that cannot be immediately updated, Palo Alto Networks recommends following best practices for securing the PAN-OS management interface as outlined in their technical documentation (Palo Alto Advisory).