CVE-2020-1998 in PAN-OS
Summary
by MITRE
An improper authorization vulnerability in PAN-OS that mistakenly uses the permissions of local linux users instead of the intended SAML permissions of the account when the username is shared for the purposes of SSO authentication. This can result in authentication bypass and unintended resource access for the user. This issue affects: PAN-OS 7.1 versions earlier than 7.1.26; PAN-OS 8.0 versions earlier than 8.0.21; PAN-OS 8.1 versions earlier than 8.1.13; PAN-OS 9.0 versions earlier than 9.0.6; PAN-OS 9.1 versions earlier than 9.1.1.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/17/2020
The vulnerability described in CVE-2020-1998 represents a critical authorization flaw in Palo Alto Networks PAN-OS firewall software that fundamentally undermines the security controls designed for single sign-on operations. This issue specifically impacts the authentication mechanisms that govern how user permissions are evaluated during SSO sessions, creating a dangerous misalignment between intended security policies and actual system behavior. The flaw manifests when the system incorrectly delegates access control decisions to local linux user permissions rather than properly enforcing the SAML-based authorization rules that should govern user access to network resources.
The technical root cause of this vulnerability lies in the improper handling of authentication contexts within the PAN-OS platform, where the system fails to correctly distinguish between local user accounts and SAML-authenticated users when username conflicts occur. This misconfiguration creates a scenario where local linux permissions take precedence over SAML permissions, effectively allowing unauthorized access to network resources that should be restricted to specific user groups or roles. The vulnerability is particularly concerning because it operates at the authorization layer, meaning that even if authentication succeeds through SSO, the system may still grant inappropriate access based on local user permissions rather than the intended SAML-based access controls.
The operational impact of this vulnerability extends far beyond simple access control issues, as it creates potential pathways for privilege escalation and unauthorized network access that could compromise entire network infrastructures. Attackers could exploit this flaw to bypass authentication mechanisms entirely, gaining access to network resources that should only be available to specific user roles or groups. This could result in unauthorized access to sensitive network data, potential lateral movement within the network, and the ability to modify or delete critical network configurations. The vulnerability affects multiple major versions of PAN-OS, indicating a widespread issue that would impact numerous organizations relying on Palo Alto firewalls for network security.
Organizations affected by this vulnerability should prioritize immediate remediation through the application of the appropriate PAN-OS patches, specifically targeting versions 7.1.26, 8.0.21, 8.1.13, 9.0.6, and 9.1.1 respectively. The mitigation strategy should include comprehensive testing of the patched systems to ensure that SSO authentication operates correctly and that proper authorization controls are restored. Additionally, security teams should conduct thorough audits of existing SSO configurations and access controls to identify any potential exploitation that may have occurred before patching. This vulnerability aligns with CWE-863, which describes improper authorization issues, and represents a clear violation of the principle of least privilege that should govern all authentication and authorization systems. From an ATT&CK perspective, this vulnerability enables techniques such as privilege escalation and credential access, making it a significant concern for organizations implementing zero-trust security models where proper authorization controls are essential for maintaining network integrity and security posture.