CVE-2021-3055: PAN-OS: XML External Entity (XXE) Reference Vulnerability in the PAN-OS Web Interface

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-09-08 · updated 2026-06-17
Weakness: CWE-611

Description

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. This issue impacts: PAN-OS 8.1 versions earlier than PAN-OS 8.1.20; PAN-OS 9.0 versions earlier than PAN-OS 9.0.14; PAN-OS 9.1 versions earlier than PAN-OS 9.1.10; PAN-OS 10.0 versions earlier than PAN-OS 10.0.6. This issue does not affect Prisma Access.

Affected products

Palo Alto Networks PAN-OS: from 8.1.0 before 8.1.20; from 9.0.0 before 9.0.14; from 9.1.0 before 9.1.10; from 10.0.0 before 10.0.6 — fixed in 8.1.20, 9.0.14, 9.1.10, 10.0.6
Palo Alto Networks PAN-OS: from 9.0 before 9.0.14; from 9.1 before 9.1.10; from 10.0 before 10.0.6; from 8.1 before 8.1.20 — fixed in 9.0.14, 9.1.10, 10.0.6, 8.1.20

How to fix

Upgrade to a fixed version: Palo Alto Networks PAN-OS 8.1.20, 9.0.14, 9.1.10, 10.0.6; Palo Alto Networks PAN-OS 9.0.14, 9.1.10, 10.0.6, 8.1.20. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2021-3055 or the next vulnerability affects your stack