CVE-2020-2050 in PAN-OS
Summary
by MITRE • 11/12/2020
An authentication bypass vulnerability exists in the GlobalProtect SSL VPN component of Palo Alto Networks PAN-OS software that allows an attacker to bypass all client certificate checks with an invalid certificate. A remote attacker can successfully authenticate as any user and gain access to restricted VPN network resources when the gateway or portal is configured to rely entirely on certificate-based authentication. Impacted features that use SSL VPN with client certificate verification are: GlobalProtect Gateway, GlobalProtect Portal, GlobalProtect Clientless VPN In configurations where client certificate verification is used in conjunction with other authentication methods, the protections added by the certificate check are ignored as a result of this issue. This issue impacts: PAN-OS 8.1 versions earlier than PAN-OS 8.1.17; PAN-OS 9.0 versions earlier than PAN-OS 9.0.11; PAN-OS 9.1 versions earlier than PAN-OS 9.1.5; PAN-OS 10.0 versions earlier than PAN-OS 10.0.1.
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Analysis
by VulDB Data Team • 12/05/2020
The vulnerability described in CVE-2020-2050 represents a critical authentication bypass flaw within Palo Alto Networks PAN-OS software's GlobalProtect SSL VPN component. This issue fundamentally undermines the security model of certificate-based authentication by allowing unauthorized access to VPN resources. The flaw specifically affects systems where client certificate verification is the sole authentication method, creating a pathway for attackers to bypass all certificate validation checks regardless of certificate validity. The vulnerability stems from improper handling of certificate validation routines within the SSL VPN implementation, where the system fails to properly enforce certificate requirements during the authentication process.
The technical nature of this flaw aligns with CWE-287, which addresses improper authentication issues in software systems. The vulnerability operates at the authentication layer of the network security infrastructure, specifically targeting the GlobalProtect Gateway, Portal, and Clientless VPN components. When exploited, the flaw enables remote attackers to authenticate as any user within the system without possessing valid client certificates, effectively rendering certificate-based authentication meaningless. This occurs because the system continues to process authentication requests even when presented with invalid certificates, failing to properly validate certificate chains and cryptographic signatures that should normally prevent unauthorized access.
The operational impact of this vulnerability is severe and far-reaching within enterprise network security environments. Organizations relying on certificate-based authentication for VPN access face significant risk of unauthorized network penetration, data exfiltration, and lateral movement attacks. The vulnerability affects multiple PAN-OS versions across different release lines, creating widespread exposure across various network security deployments. Security teams must recognize that this flaw can be exploited without requiring additional privileges or complex attack vectors, making it particularly dangerous in environments where certificate-based authentication is considered a primary security control. The impact extends beyond simple unauthorized access to include potential compromise of sensitive network resources and violation of security policies that depend on certificate validation.
Organizations should implement immediate mitigations including upgrading to the patched versions specified in the advisory, specifically PAN-OS 8.1.17, 9.0.11, 9.1.5, and 10.0.1. The ATT&CK framework categorizes this vulnerability under privilege escalation and initial access techniques, as it allows attackers to establish persistent network presence through unauthorized authentication. Network administrators should also consider implementing additional monitoring and detection mechanisms to identify potential exploitation attempts, as the vulnerability may not generate obvious audit trail entries. The security community recognizes this as a critical vulnerability requiring immediate remediation, as it directly undermines the trust model that certificate-based authentication is designed to provide. Organizations with configurations that combine certificate authentication with other methods should verify that the certificate checks are properly enforced, as the flaw may cause the system to ignore certificate validation even when other authentication factors are present.