CVE-2020-1999: Palo Alto Networks PAN-OS

Medium severity, CVSS 5.3. EPSS: 1.3% chance of exploitation in the next 30 days.

A vulnerability exists in the Palo Alto Network PAN-OS signature-based threat detection engine that allows an attacker to communicate with devices in the network in a way that is not analyzed for threats by sending data through specifically crafted TCP packets. This technique evades signature-based threat detection. This issue impacts: PAN-OS 8.1 versions earlier than 8.1.17; PAN-OS 9.0 versions earlier than 9.0.11; PAN-OS 9.1 versions earlier than 9.1.5; All versions of PAN-OS 7.1 and PAN-OS 8.0.

Affected products

• Palo Alto Networks PAN-OS: from 7.1.0, up to and including 7.1.26; from 8.0.0, up to and including 8.0.20; from 8.1.0, before 8.1.17 (fixed in 8.1.17); from 9.0.0, before 9.0.11 (fixed in 9.0.11); from 9.1.0, before 9.1.5 (fixed in 9.1.5)

Published 2020-11-12. Last modified 2026-06-17.