Palo Alto Networks Security Advisories / CVE-2021-3055

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

Severity 6.5 · MEDIUM
Attack Vector NETWORK
Attack Complexity LOW
Confidentiality Impact HIGH
Privileges Required HIGH
Integrity Impact NONE
User Interaction NONE
Availability Impact HIGH


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.

Product Status

PAN-OS 10.1None10.1.*
PAN-OS 10.0< 10.0.6>= 10.0.6
PAN-OS 9.1< 9.1.10>= 9.1.10
PAN-OS 9.0< 9.0.14>= 9.0.14
PAN-OS 8.1< 8.1.20>= 8.1.20

Severity: MEDIUM

CVSSv3.1 Base Score: 6.5 (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:H)

Exploitation Status

Palo Alto Networks is not aware of any malicious attempts to exploit this vulnerability.

Weakness Type

CWE-611 Improper Restriction of XML External Entity Reference ('XXE')


This issue is fixed in PAN-OS 8.1.20, PAN-OS 9.0.14, PAN-OS 9.1.10, PAN-OS 10.0.6, and all later PAN-OS versions.

Workarounds and Mitigations

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


Palo Alto Networks thanks Cristian Mocanu and Dan Marin of Deloitte for discovering and reporting this issue.


Added threat prevention workaround for the vulnerability
Initial publication
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