CVE-2015-8955 in Linux
Summary
by MITRE
arch/arm64/kernel/perf_event.c in the Linux kernel before 4.1 on arm64 platforms allows local users to gain privileges or cause a denial of service (invalid pointer dereference) via vectors involving events that are mishandled during a span of multiple HW PMUs.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability identified as CVE-2015-8955 resides within the Linux kernel's arm64 architecture implementation, specifically in the perf_event.c file that manages performance monitoring unit events. This flaw affects Linux kernel versions prior to 4.1 and represents a critical security weakness that can be exploited by local attackers to either escalate privileges or execute denial of service attacks. The vulnerability stems from improper handling of performance monitoring events during operations spanning multiple hardware performance monitoring units, creating a scenario where invalid pointer dereferences can occur. The technical nature of this vulnerability places it squarely within the realm of kernel-level memory corruption issues that can lead to system instability or unauthorized access.
The core technical flaw manifests when the kernel processes performance monitoring events across multiple hardware PMUs, where the event handling code fails to properly validate or manage pointers during the transition between different monitoring units. This mismanagement results in a situation where a local user can craft specific performance monitoring events that trigger invalid memory access patterns, leading to either privilege escalation or system crashes. The vulnerability is particularly concerning because it operates at the kernel level, where the attacker's control over the system's core operations can result in complete system compromise. This issue falls under the CWE-125 vulnerability category, which deals with out-of-bounds read conditions, and aligns with ATT&CK technique T1068, which involves exploiting legitimate credentials and privileges to gain system access.
The operational impact of CVE-2015-8955 extends beyond simple denial of service scenarios, as local users can potentially leverage this vulnerability to escalate their privileges from standard user level to root access, effectively compromising the entire system. The vulnerability's exploitation requires local access to the system but does not necessitate network connectivity, making it particularly dangerous in environments where local user access is not properly restricted. Attackers can utilize this flaw to execute arbitrary code with kernel-level privileges, potentially leading to complete system takeover. The performance monitoring subsystem's integration with the kernel's security model means that successful exploitation can bypass traditional security controls and access critical system resources. Organizations running vulnerable kernel versions on arm64 platforms face significant risk, as this vulnerability can be exploited without requiring special tools or network access, making it a particularly attractive target for malicious actors. The mitigation strategy involves upgrading to Linux kernel version 4.1 or later, where the improper pointer handling has been corrected through enhanced validation and proper memory management practices. Additionally, system administrators should implement strict access controls to limit local user privileges and monitor for unusual performance monitoring activity that might indicate exploitation attempts.