Pierluigi Paganini June 30, 2020

U.S. Cyber Command believes foreign APTs will likely attempt to exploit the recently addressed flaw in Palo Alto Networks’s PAN-OS firewall OS.

Recently Palo Alto Network addressed a critical vulnerability, tracked as CVE-2020-2021, affecting the PAN-OS operating system that powers its next-generation firewall. The flaw could allow unauthenticated network-based attackers to bypass authentication, it has has been rated as critical severity and received a CVSS 3.x base score of 10.

According to Palo Alto Networks the vulnerability impacts 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 doesn’t affect PAN-OS 7.1.

The company confirmed that the vulnerability cannot be exploited if SAML is not used for authentication and if the ‘Validate Identity Provider Certificate’ option is enabled (checked) in the SAML Identity Provider Server Profile.

“When Security Assertion Markup Language (SAML) authentication is enabled and the ‘Validate Identity Provider Certificate’ option is disabled (unchecked), improper verification of signatures in PAN-OS SAML authentication enables an unauthenticated network-based attacker to access protected resources,” reads the security advisory published by the company. “The attacker must have network access to the vulnerable server to exploit this vulnerability.” “In the case of GlobalProtect Gateways, GlobalProtect Portal, Clientless VPN, Captive Portal, and Prisma Access, an unauthenticated attacker with network access to the affected servers can gain access to protected resources if allowed by configured authentication and Security policies,” 

In attacks against PAN-OS and Panorama web interfaces, this vulnerability could be exploited by an unauthenticated attacker with network access to log in as an administrator and perform administrative actions.

CERT/CC analyst Will Dormann noticed that some identity service providers suggest customers use configuration that could be exploited by attackers to trigger the issue.

The good news is that Palo Alto Networks is not aware of attacks in the wild exploiting this vulnerability.

Admins could determine if their installs are vulnerable following the instructions provided by the company in a knowledge base article.

The USCYBERCOM believes that nation-state actors will likely attempt to exploit the vulnerability in Palo Alto Networks’ firewall very soon.

“Please patch all devices affected by CVE-2020-2021 immediately, especially if SAML is in use,” US Cyber Command said in a tweet.

“Foreign APTs will likely attempt [to] exploit soon.”

Pierluigi Paganini

(SecurityAffairs – hacking, Palo Alto Networks)

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