CVE-2021-3031: Palo Alto Networks PAN-OS

Medium severity, CVSS 4.3. EPSS: 0.5% chance of exploitation in the next 30 days.

Padding bytes in Ethernet packets on PA-200, PA-220, PA-500, PA-800, PA-2000 Series, PA-3000 Series, PA-3200 Series, PA-5200 Series, and PA-7000 Series firewalls are not cleared before the data frame is created. This leaks a small amount of random information from the firewall memory into the Ethernet packets. An attacker on the same Ethernet subnet as the PAN-OS firewall is able to collect potentially sensitive information from these packets. This issue is also known as Etherleak and is detected by security scanners as CVE-2003-0001. This issue impacts: PAN-OS 8.1 version earlier than PAN-OS 8.1.18; PAN-OS 9.0 versions earlier than PAN-OS 9.0.12; PAN-OS 9.1 versions earlier than PAN-OS 9.1.5.

Affected products

• Palo Alto Networks PAN-OS: from 8.1.0, before 8.1.18 (fixed in 8.1.18); from 9.0.0, before 9.0.12 (fixed in 9.0.12); from 9.1.0, before 9.1.5 (fixed in 9.1.5)

Published 2021-01-13. Last modified 2026-06-17.