SCAVY, a newly unveiled framework, aims to automate the discovery of memory corruption targets within the Linux kernel, a crucial step in detecting privilege escalation exploits. These types of exploits often target memory corruption vulnerabilities to gain unauthorized access to system resources. Identifying these memory targets has traditionally been a time-consuming and manual task, focusing mainly on specific elements such as function pointers. SCAVY, however, significantly broadens the scope of kernel data structure analysis, addressing the approximately 90% of structures that were previously overlooked.
The SCAVY framework is designed to be bug-type agnostic, meaning it can analyze a wider range of vulnerabilities beyond those typically identified in manual scans. It uses advanced techniques like fuzzing and differential analysis to identify which fields, when corrupted, lead to privilege escalation. This allows SCAVY to find exploitable memory corruption targets across a much broader spectrum of kernel data structures, greatly increasing the potential attack surface for analysis. The framework’s ability to perform automated differential analysis enables it to detect vulnerabilities that are often difficult to identify through traditional methods.
SCAVY operates in three primary phases: instrumentation and analysis, discovery of potential memory targets, and detection of privilege escalation.
The first phase involves mapping allocated memory addresses to their corresponding data types, ensuring accurate identification of kernel structure layouts.
The discovery phase uses fuzzing to corrupt fields within kernel structures, observing the system’s behavior to identify potential memory targets. Finally, SCAVY checks whether these corrupted fields allow unauthorized access to privileged resources, such as enabling unprivileged processes to perform root-level operations.
The SCAVY framework has already demonstrated significant success, identifying 17 new exploitable fields and generating 955 proof-of-concept exploits. These findings have led to the creation of fully functional exploits targeting several CVEs, bypassing key kernel defenses like Kernel Address Space Layout Randomization (KASLR) and Supervisor Mode Execution Prevention (SMEP). The tool not only helps in offensive security but also provides valuable insights for defenders to implement mitigations, reducing the attack surface for future exploits. Although challenges remain, such as automating multi-field corruption analysis, SCAVY’s capabilities are set to enhance Linux kernel security and provide broader protection against privilege escalation attacks.
