CVE-2016-4558 in Linux
Summary
by MITRE
The BPF subsystem in the Linux kernel before 4.5.5 mishandles reference counts, which allows local users to cause a denial of service (use-after-free) or possibly have unspecified other impact via a crafted application on (1) a system with more than 32 Gb of memory, related to the program reference count or (2) a 1 Tb system, related to the map reference count.
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Analysis
by VulDB Data Team • 09/27/2024
The vulnerability identified as CVE-2016-4558 represents a critical flaw in the Linux kernel's Berkeley Packet Filter (BPF) subsystem that affects versions prior to 4.5.5. This issue stems from improper handling of reference counts within the kernel's memory management mechanisms, creating a condition where the kernel fails to properly track object lifecycles. The BPF subsystem serves as a powerful network packet filtering and tracing mechanism within the Linux kernel, enabling efficient packet classification and monitoring capabilities that are essential for network security and system monitoring operations. When reference counting mechanisms fail, the kernel may prematurely free memory objects while still in use, leading to unpredictable behavior and potential security implications.
The technical flaw manifests in two distinct scenarios based on system memory configuration. On systems with more than 32 gigabytes of memory, the vulnerability occurs due to improper handling of program reference counts within the BPF subsystem. This specific condition arises because the kernel's reference counting logic fails to properly account for BPF programs when they are loaded or executed on memory configurations exceeding the 32 gigabyte threshold. Similarly, on systems with 1 terabyte of memory, the vulnerability manifests through improper map reference count handling, where BPF map objects are not properly tracked during their lifecycle. Both scenarios involve use-after-free conditions that occur when the kernel attempts to access memory locations that have already been freed, creating opportunities for system instability and potential privilege escalation.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can potentially enable unspecified other impacts that may include privilege escalation or system compromise. Local attackers with access to the system can craft malicious applications that exploit these reference count handling flaws to trigger the use-after-free conditions. The vulnerability is particularly concerning because it affects systems with substantial memory configurations, which are common in enterprise environments and high-performance computing scenarios. When exploited, these conditions can cause kernel memory corruption that leads to system crashes, reboot cycles, or potentially provide attackers with opportunities to execute arbitrary code with kernel privileges. The attack vector requires local system access but does not necessitate elevated privileges, making it a significant concern for system administrators who must ensure proper kernel patching across their infrastructure.
Mitigation strategies for CVE-2016-4558 primarily focus on immediate kernel version updates to 4.5.5 or later, which contain the necessary fixes for the reference counting implementation. System administrators should prioritize patching affected systems, particularly those with large memory configurations where the vulnerability is most likely to manifest. Additionally, monitoring for unusual system behavior or frequent kernel crashes can help detect exploitation attempts. The vulnerability aligns with CWE-415, which addresses improper handling of reference counts leading to double-free conditions, and CWE-476, which covers null pointer dereferences that can occur when reference counting fails. From an ATT&CK framework perspective, this vulnerability maps to T1068, which involves privilege escalation through kernel exploits, and T1499, which encompasses denial of service attacks targeting system resources. Organizations should implement comprehensive patch management procedures to prevent exploitation and maintain system integrity across their network infrastructure.