CVE-2017-9986 in Linux
Summary
by MITRE
The intr function in sound/oss/msnd_pinnacle.c in the Linux kernel through 4.11.7 allows local users to cause a denial of service (over-boundary access) or possibly have unspecified other impact by changing the value of a message queue head pointer between two kernel reads of that value, aka a "double fetch" vulnerability.
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Analysis
by VulDB Data Team • 08/10/2025
The vulnerability identified as CVE-2017-9986 resides within the Linux kernel's OSS (Open Sound System) subsystem, specifically in the sound/oss/msnd_pinnacle.c file. This flaw represents a classic double fetch vulnerability that exploits a race condition in kernel memory management. The issue manifests when the intr function processes message queue operations where a pointer value is read twice within a critical section, creating an opportunity for malicious local users to manipulate kernel state between these two reads. The vulnerability falls under CWE-367 which categorizes time-of-check to time-of-use errors, where the state of a resource changes between verification and actual usage phases.
The technical exploitation of this vulnerability occurs through a carefully orchestrated sequence where an attacker modifies the message queue head pointer value between two kernel reads. This manipulation creates a scenario where the first read retrieves a valid pointer value while the second read accesses an altered or invalid pointer, leading to memory access violations. The kernel's handling of the msnd_pinnacle sound driver, which supports certain Pinnacle sound cards, becomes compromised when processing audio data through the affected message queue mechanism. This particular driver implementation fails to properly synchronize access to the queue head pointer, allowing for a window where external interference can cause memory corruption.
The operational impact of this vulnerability extends beyond simple denial of service, though DoS represents the most immediate consequence. Local attackers can leverage this weakness to trigger memory corruption that may lead to system instability, kernel panics, or potentially more severe security implications depending on the execution context. The double fetch pattern creates a condition where memory boundaries are exceeded, potentially allowing for arbitrary code execution or privilege escalation within the kernel space. This vulnerability demonstrates the critical importance of proper synchronization mechanisms in kernel code, particularly when dealing with shared data structures that are accessed by multiple code paths or contexts.
Mitigation strategies for CVE-2017-9986 require immediate kernel updates to versions containing the patched msnd_pinnacle driver implementation. System administrators should prioritize applying the relevant security patches from their respective Linux distributions, as the vulnerability affects kernel versions through 4.11.7. The fix typically involves implementing proper locking mechanisms around the message queue head pointer access, ensuring that the pointer value remains consistent between the two reads. Additionally, organizations should consider implementing kernel hardening measures such as stack canaries, address space layout randomization, and kernel address space protection features that can limit the impact of such vulnerabilities. This vulnerability aligns with ATT&CK technique T1068 which covers local privilege escalation through kernel exploits, emphasizing the need for comprehensive kernel security measures in enterprise environments.
The broader implications of this vulnerability highlight the persistent challenges in kernel security, particularly with legacy drivers that may not have received adequate security review or modernization. The msnd_pinnacle driver represents a piece of older hardware support code that has remained in kernel trees without sufficient security auditing. This case demonstrates how seemingly minor implementation flaws in kernel subsystems can create significant security risks, especially when dealing with shared memory operations and race conditions. Organizations should conduct regular security assessments of their kernel configurations and ensure that legacy drivers are either properly maintained or deprecated in favor of more secure alternatives. The vulnerability also underscores the importance of maintaining up-to-date kernel versions and implementing robust security monitoring to detect potential exploitation attempts.