PAN-OS: XML External Entity (XXE) Reference Vulnerability in the PAN-OS Web Interface

An improper restriction of XML external entity (XXE) reference vulnerability in the Palo Alto Networks PAN-OS web interface enables an authenticated administrator to read any arbitrary file from the file system and send a specifically crafted request to the firewall that causes the service to crash. 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.

Work around:
Enable signatures for Unique Threat ID 91588 on traffic destined for the web interface to block attacks against CVE-2021-3055.

This issue requires the attacker to have authenticated access to the PAN-OS web interface. You can mitigate the impact of this issue by following best practices for securing the PAN-OS web interface. Please review the Best Practices for Securing Administrative Access in the PAN-OS technical documentation at https://docs.paloaltonetworks.com/best-practices.