CVE-2015-9004 in Linux
Summary
by MITRE • 01/25/2023
kernel/events/core.c in the Linux kernel before 3.19 mishandles counter grouping, which allows local users to gain privileges via a crafted application, related to the perf_pmu_register and perf_event_open functions.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2015-9004 resides within the Linux kernel's performance monitoring subsystem, specifically in the kernel/events/core.c file. This flaw affects Linux kernel versions prior to 3.19 and represents a critical privilege escalation vulnerability that can be exploited by local attackers through carefully crafted applications. The issue stems from improper handling of counter grouping mechanisms within the performance monitoring infrastructure, which forms a fundamental component of the kernel's profiling and monitoring capabilities.
The technical root cause of this vulnerability lies in how the perf_pmu_register and perf_event_open functions process performance monitoring unit groupings. When multiple performance counters are grouped together for monitoring purposes, the kernel fails to properly validate or enforce access controls during the registration and opening processes. This mismanagement creates a scenario where a local user can manipulate the grouping of performance counters in a way that bypasses normal privilege checks and access restrictions. The flaw essentially allows an unprivileged user to construct malicious performance monitoring events that can escalate their privileges to root level access.
From an operational perspective, this vulnerability presents a severe threat to Linux systems as it requires no network connectivity or external attack vectors. The exploit can be executed entirely locally, making it particularly dangerous in multi-user environments where privilege separation is critical. The attack vector leverages the legitimate performance monitoring infrastructure that is typically enabled on most Linux systems, making detection more challenging. Security researchers have classified this as a local privilege escalation vulnerability with a CVSS score indicating high severity, as it can be exploited without any special privileges or network access.
The impact of this vulnerability extends beyond simple privilege escalation, as it can potentially allow attackers to gain full system control, access sensitive data, modify system files, and establish persistent access. The affected functions are commonly used in system monitoring, profiling, and debugging scenarios, meaning that the vulnerability can be triggered through normal system operations. This makes the attack surface broader than initially apparent, as legitimate applications may inadvertently trigger the vulnerable code paths.
Organizations should implement immediate mitigations including kernel updates to versions 3.19 or later where this vulnerability has been addressed. System administrators should also consider implementing additional security controls such as restricting access to performance monitoring interfaces for non-privileged users and monitoring for unusual performance event registration patterns. The vulnerability aligns with CWE-276, which describes improper privileges, and can be mapped to ATT&CK technique T1068, privilege escalation through local exploitation. Additionally, this issue demonstrates the importance of proper input validation and access control mechanisms in kernel-level code, particularly in subsystems that handle performance monitoring and system profiling operations.
The fix for this vulnerability involved correcting the validation logic in the performance monitoring subsystem to properly enforce access controls when handling counter grouping operations. The kernel developers implemented additional checks to ensure that performance event registration and opening operations respect the appropriate privilege levels and do not allow unauthorized access to system monitoring resources. This patch demonstrates the critical importance of maintaining proper security boundaries even within legitimate system components that are typically considered safe or trusted.