On June 29, 2020 Palo Alto Networks published a notice about a critical vulnerability affecting their devices. https://security.paloaltonetworks.com/CVE-2020-2021.

The vulnerability, which is listed as an issue affecting the way SAML (Security Assertion Markup Language) authentication happens, can be exploited by remote attackers to gain access to the device. Dissecting this vulnerability, Palo Alto states that it can only be exploited if the device is configured in a particular way.

Firstly, if you are not using SAML-based authentication, you can stop reading here because you are not affected. However, if you are using SAML-based authentication, this vulnerability applies if:

  • The “Validate Identity Provider Certificate” option is not enabled (or not checked) in the SAML Identity Provider Server Profile.

Resources that are affected include:

  • GlobalProtect Gateway,
  • GlobalProtect Portal,
  • GlobalProtect Clientless VPN,
  • Authentication and Captive Portal,
  • PAN-OS next-generation firewalls (PA-Series, VM-Series) and Panorama web interfaces,
  • Prisma Access

The PA version that are affected include: PAN-OS 9.1 versions earlier than PAN-OS 9.1.3; PAN-OS 9.0 versions earlier than PAN-OS 9.0.9; PAN-OS 8.1 versions earlier than PAN-OS 8.1.15, and all versions of PAN-OS 8.0 (EOL). This issue does not affect PAN-OS 7.1.

Palo alto provides the following remediation

  • Detailed descriptions of how to check for the configuration required for exposure and mitigate them are listed in the knowledge base article https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA14u0000008UXK.
  • To check whether SAML authentication is enabled on a firewall, see the configuration under Device > Server Profiles > SAML Identity Provider.
  • To check whether SAML authentication is enabled for Panorama administrator authentication, see the configuration under Panorama> Server Profiles > SAML Identity Provider
  • To check whether SAML authentication is enabled for firewalls managed by Panorama, see the configuration under Device > [template]> Server Profiles > SAML Identity Provider.

Please review your firewall configurations to ensure you are not affected by this vulnerability.