CVE-2020-1992 in PAN-OS
Summary
by MITRE
A format string vulnerability in the Varrcvr daemon of PAN-OS on PA-7000 Series devices with a Log Forwarding Card (LFC) allows remote attackers to crash the daemon creating a denial of service condition or potentially execute code with root privileges. This issue affects Palo Alto Networks PAN-OS 9.0 versions before 9.0.7; PAN-OS 9.1 versions before 9.1.2 on PA-7000 Series devices with an LFC installed and configured. This issue requires WildFire services to be configured and enabled. This issue does not affect PAN-OS 8.1 and earlier releases. This issue does not affect any other PA Series firewalls.
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Analysis
by VulDB Data Team • 05/18/2024
The vulnerability identified as CVE-2020-1992 represents a critical format string flaw within the Varrcvr daemon component of Palo Alto Networks PAN-OS operating systems. This daemon specifically handles log forwarding functionality on PA-7000 series devices equipped with Log Forwarding Cards, making it a significant target for attackers seeking to compromise network security infrastructure. The vulnerability manifests as a classic format string vulnerability that occurs when user-supplied input is improperly processed through printf-style functions without proper sanitization, creating opportunities for attackers to manipulate memory layout and execution flow.
The technical exploitation of this vulnerability occurs through crafted input that is processed by the Varrcvr daemon during log forwarding operations. When WildFire services are enabled and configured on affected PA-7000 Series devices, attackers can leverage this format string vulnerability to either crash the daemon service, resulting in denial of service conditions that disrupt network monitoring capabilities, or potentially execute arbitrary code with root privileges. This dual nature of impact makes the vulnerability particularly dangerous as it can transition from simple service disruption to full system compromise. The vulnerability is specifically confined to PAN-OS versions 9.0.x before 9.0.7 and 9.1.x before 9.1.2, with the critical restriction that it only affects devices with LFC cards installed and configured, excluding all other PA Series firewall models.
The operational impact of CVE-2020-1992 extends beyond simple service disruption to potentially enable complete system compromise of affected network infrastructure. Network administrators responsible for maintaining PA-7000 Series devices with LFC cards face significant risk of unauthorized access and potential data exfiltration if this vulnerability remains unpatched. The requirement for WildFire services to be configured and enabled means that organizations with comprehensive threat intelligence capabilities are particularly vulnerable, as these services are often essential for modern security operations. This vulnerability directly aligns with CWE-134, which categorizes format string vulnerabilities as weaknesses that occur when format strings are constructed using user input without proper validation or sanitization. The attack surface is further constrained by the specific device and software version requirements, but this also makes the vulnerability more predictable for attackers who can identify affected systems through network reconnaissance.
Organizations affected by this vulnerability should implement immediate mitigation strategies while planning for proper patching operations. The most effective immediate response involves disabling WildFire services on affected devices until patches are deployed, though this may compromise threat detection capabilities. Network segmentation and access controls should be strengthened around affected devices to limit potential attack vectors, as outlined in ATT&CK technique T1068 which addresses local privilege escalation and T1499 which covers network disruption attacks. The vulnerability's requirement for specific PAN-OS versions and hardware configurations means that organizations can more easily identify affected systems through inventory management and vulnerability scanning processes. Security teams should also implement enhanced monitoring of Varrcvr daemon processes and log forwarding activities to detect potential exploitation attempts. Regular patch management procedures should be prioritized to ensure all affected PAN-OS installations receive the necessary security updates, particularly focusing on the specific version releases mentioned in the vulnerability advisory. The remediation process must consider potential service disruptions during patch deployment and maintain rollback procedures to ensure network availability during the update process.