CVE-2020-2002 in PAN-OS
Summary
by MITRE
An authentication bypass by spoofing vulnerability exists in the authentication daemon and User-ID components of Palo Alto Networks PAN-OS by failing to verify the integrity of the Kerberos key distribution center (KDC) before authenticating users. This affects all forms of authentication that use a Kerberos authentication profile. A man-in-the-middle type of attacker with the ability to intercept communication between PAN-OS and KDC can login to PAN-OS as an administrator. 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.
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Analysis
by VulDB Data Team • 10/17/2020
This vulnerability represents a critical authentication bypass flaw in Palo Alto Networks PAN-OS devices that stems from insufficient verification of Kerberos key distribution center integrity during the authentication process. The vulnerability exists within the authentication daemon and User-ID components where the system fails to validate the authenticity of the Kerberos KDC before proceeding with user authentication. This fundamental weakness creates an exploitable condition where malicious actors can spoof authentication requests and gain administrative access to the firewall system.
The technical flaw manifests as a failure to implement proper certificate validation and integrity checks when communicating with the Kerberos KDC. This allows attackers to perform man-in-the-middle attacks by intercepting and manipulating the communication between PAN-OS devices and the KDC infrastructure. The vulnerability specifically affects all authentication mechanisms that rely on Kerberos authentication profiles, making it particularly dangerous as it undermines the core security foundation of the authentication system. According to CWE-310, this represents a weakness in cryptographic key handling where the system fails to properly validate the authenticity of cryptographic components.
The operational impact of this vulnerability is severe and far-reaching for organizations relying on Palo Alto Networks firewalls. An attacker with network access and the ability to intercept traffic can potentially escalate privileges to administrator level access without proper credentials, effectively bypassing the entire authentication framework. This creates a persistent backdoor that can be exploited for lateral movement, data exfiltration, and complete compromise of the network security infrastructure. The vulnerability affects multiple PAN-OS versions including 7.1.26, 8.0.21, 8.1.13, and 9.0.6, indicating a widespread issue that has persisted across several major releases.
The attack vector for this vulnerability aligns with ATT&CK technique T1550.001, which describes the use of valid accounts for unauthorized access through credential manipulation. Attackers can leverage this flaw to establish persistent access to network security controls, potentially remaining undetected for extended periods while maintaining administrative privileges. The vulnerability's exploitation requires network interception capabilities and knowledge of the Kerberos authentication protocol, making it moderately difficult to exploit but highly impactful when successful.
Organizations should implement immediate mitigations including upgrading to the patched versions of PAN-OS as specified in the advisory, enabling proper certificate validation mechanisms, and implementing network segmentation to limit the attack surface. Additional defensive measures include monitoring for unusual authentication patterns, implementing network traffic analysis to detect man-in-the-middle activities, and ensuring proper network infrastructure security to prevent interception of Kerberos communications. The vulnerability demonstrates the critical importance of proper cryptographic validation and integrity checking in authentication systems, aligning with security best practices outlined in NIST SP 800-57 for cryptographic key management and validation.