CVE-2017-17863 in Linux
Summary
by MITRE
kernel/bpf/verifier.c in the Linux kernel 4.9.x through 4.9.71 does not check the relationship between pointer values and the BPF stack, which allows local users to cause a denial of service (integer overflow or invalid memory access) or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 01/19/2023
The vulnerability identified as CVE-2017-17863 resides within the Linux kernel's BPF (Berkeley Packet Filter) verifier component, specifically in the kernel/bpf/verifier.c file. This flaw affects Linux kernel versions 4.9.x through 4.9.71, representing a critical security issue that undermines the kernel's ability to properly validate pointer operations within the BPF execution environment. The BPF subsystem serves as a powerful networking and tracing framework that allows userspace applications to execute sandboxed programs directly within the kernel space, making it a crucial component for system security and performance monitoring.
The technical root cause of this vulnerability stems from the absence of proper validation checks between pointer values and BPF stack memory locations during the verification phase of BPF program execution. When BPF programs are loaded into the kernel, the verifier performs essential checks to ensure program safety and prevent memory corruption. However, this particular flaw fails to validate the relationship between pointer arithmetic and stack memory boundaries, creating a scenario where malicious pointer operations can bypass these critical safety mechanisms. The vulnerability manifests as a potential integer overflow condition or invalid memory access that occurs when pointer calculations exceed expected bounds or reference invalid memory locations within the BPF stack.
The operational impact of this vulnerability extends beyond simple denial of service conditions, presenting potential for more severe consequences including system instability and unauthorized privilege escalation. Local attackers with the ability to load BPF programs can exploit this weakness to trigger integer overflow conditions that may result in kernel memory corruption, ultimately leading to system crashes or potentially allowing attackers to execute arbitrary code with kernel privileges. This represents a significant escalation from typical denial of service scenarios, as the vulnerability could be leveraged to compromise the entire system integrity. The BPF subsystem's role in network packet filtering and system tracing makes this particularly dangerous, as it provides an attack surface that could be exploited to monitor network traffic or manipulate system behavior.
From a cybersecurity perspective, this vulnerability aligns with CWE-191, which addresses integer underflow and overflow conditions, and demonstrates characteristics consistent with ATT&CK technique T1059.006 for kernel-mode rootkits and privilege escalation. The flaw represents a classic case of insufficient input validation within kernel space, where the absence of proper boundary checking creates exploitable conditions for memory corruption attacks. Organizations should prioritize immediate patching of affected kernel versions to prevent exploitation, while security teams should monitor for potential indicators of compromise related to BPF program loading activities and unusual kernel memory access patterns. The vulnerability underscores the critical importance of thorough verification processes in kernel-space code and highlights the necessity of comprehensive security testing for system components that operate with elevated privileges and direct hardware access capabilities.