CVE-2020-2041 in PAN-OS
Summary
by MITRE
An insecure configuration of the appweb daemon of Palo Alto Networks PAN-OS 8.1 allows a remote unauthenticated user to send a specifically crafted request to the device that causes the appweb service to crash. Repeated attempts to send this request result in denial of service to all PAN-OS services by restarting the device and putting it into maintenance mode. This issue impacts all versions of PAN-OS 8.0, and PAN-OS 8.1 versions earlier than 8.1.16.
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Analysis
by VulDB Data Team • 09/09/2020
The vulnerability described in CVE-2020-2041 represents a critical denial of service weakness within the appweb daemon of Palo Alto Networks PAN-OS 8.1 platforms. This security flaw stems from an insecure configuration that permits remote unauthenticated attackers to exploit a specific request pattern that causes the appweb service to crash. The vulnerability specifically affects PAN-OS 8.0 and 8.1 versions prior to 8.1.16, creating a significant operational risk for organizations relying on these network security platforms. The issue manifests through a crafted request that can be sent to the device without requiring authentication credentials, making it particularly dangerous as it can be exploited by any remote attacker with network access to the affected system.
The technical exploitation of this vulnerability involves sending a carefully constructed request to the appweb daemon which triggers a service crash condition. This crash does not simply terminate the appweb process but rather causes a cascading failure that affects the entire PAN-OS service ecosystem. The service disruption is severe enough that repeated exploitation attempts can force the device to restart automatically and enter maintenance mode, effectively rendering all PAN-OS services unavailable. This behavior aligns with CWE-119 which addresses improper access to memory locations, and represents a classic example of how a single vulnerable service can compromise the entire system's availability. The vulnerability demonstrates poor input validation and error handling within the appweb daemon, as it fails to properly sanitize or reject malformed requests that could cause the service to behave unpredictably.
The operational impact of CVE-2020-2041 extends beyond simple service disruption to encompass complete system unavailability and potential business continuity issues. Organizations using affected PAN-OS versions face the risk of unauthorized parties gaining the ability to systematically disable their network security infrastructure through simple network requests. This creates a significant risk for network availability, as the device enters maintenance mode which typically requires manual intervention to restore normal operations. The vulnerability affects the core network security functionality of Palo Alto devices, potentially leaving networks exposed to attacks during the maintenance period. This type of attack aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and represents a serious threat to network infrastructure availability. The impact is particularly severe because the vulnerability does not require authentication, making it accessible to any remote attacker who can reach the device on the network.
Organizations should immediately implement mitigation strategies to address this vulnerability, beginning with upgrading to PAN-OS 8.1.16 or later versions where the issue has been resolved. Network segmentation and access controls should be enhanced to limit exposure of affected devices to untrusted networks, reducing the attack surface for potential exploitation attempts. The implementation of intrusion detection systems that can monitor for suspicious request patterns may provide early warning of exploitation attempts. Security teams should also consider implementing temporary network restrictions that limit access to the appweb service ports from untrusted networks. Additionally, organizations should conduct thorough vulnerability assessments to ensure all PAN-OS devices are properly updated and that no other insecure configurations exist within their network security infrastructure. The vulnerability highlights the importance of proper service hardening and input validation practices, and organizations should review their overall security posture to prevent similar issues in other network services. Regular security updates and patch management processes should be prioritized to maintain protection against known vulnerabilities.