CVE-2020-12866 in Backend
Summary
by MITRE
A NULL pointer dereference in SANE Backends before 1.0.30 allows a malicious device connected to the same local network as the victim to cause a denial of service, GHSL-2020-079.
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Analysis
by VulDB Data Team • 10/27/2020
The vulnerability identified as CVE-2020-12866 represents a critical NULL pointer dereference flaw within the SANE (Scanner Access Now Easy) backends component, specifically affecting versions prior to 1.0.30. This issue arises from inadequate input validation and error handling mechanisms within the scanning subsystem that processes device communications. The vulnerability is particularly concerning because it can be exploited remotely through a malicious device on the same local network, making it a significant threat vector for network-based attacks. The SANE backends serve as the foundation for scanner communication in Unix-like systems and numerous Linux distributions, providing a standardized interface for various scanning devices. When a malicious device attempts to establish communication with a vulnerable SANE backend system, the flawed implementation fails to properly validate incoming data structures, leading to a situation where a NULL pointer is dereferenced during the device enumeration process. This fundamental programming error occurs when the system attempts to access memory through a pointer that has not been properly initialized or has been set to NULL, causing the application to crash and resulting in a denial of service condition.
The technical exploitation of this vulnerability operates through a specific attack vector that leverages the network accessibility of SANE backends. When a malicious device connects to the same local network as a victim system running vulnerable SANE backends, it can send specially crafted communication packets designed to trigger the NULL pointer dereference condition. The flaw manifests during the device discovery and communication initialization phases where the backend system attempts to process device information from the network. This vulnerability directly maps to CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. The operational impact extends beyond simple service disruption as this vulnerability can be exploited by unauthenticated attackers within the local network segment, potentially allowing for persistent denial of service attacks against scanning services. The vulnerability affects systems that rely on SANE for scanner functionality, including but not limited to print servers, document management systems, and various networked computing environments where scanner access is required. Given the widespread adoption of SANE backends across multiple Linux distributions and Unix-based systems, the potential attack surface is extensive, making this vulnerability particularly dangerous in enterprise environments where scanning capabilities are frequently utilized.
The mitigation strategies for CVE-2020-12866 primarily focus on immediate software updates and system hardening measures. Organizations should prioritize upgrading to SANE backends version 1.0.30 or later, which contains the necessary patches to address the NULL pointer dereference issue. Network segmentation and access control measures should be implemented to limit the exposure of SANE backend services to untrusted networks, particularly in environments where scanner access is not required from external sources. The vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and more specifically with T1071.004 related to application layer protocols. System administrators should also consider implementing network monitoring solutions that can detect anomalous scanning device behavior and potential exploitation attempts. Additional defensive measures include disabling unnecessary scanning services when not actively needed, implementing firewall rules to restrict access to SANE backend ports, and conducting regular security assessments of scanning infrastructure to identify potential vulnerabilities. The patch resolution for this vulnerability demonstrates the importance of proper input validation and error handling in network services, particularly those that must process untrusted data from networked devices. Organizations should also consider implementing intrusion detection systems that can identify patterns consistent with the exploitation of similar NULL pointer dereference vulnerabilities, as these often represent early indicators of more sophisticated attacks targeting system stability and availability.