CVE-2017-15951 in Linux
Summary
by MITRE • 01/25/2023
The KEYS subsystem in the Linux kernel before 4.13.10 does not correctly synchronize the actions of updating versus finding a key in the "negative" state to avoid a race condition, which allows local users to cause a denial of service or possibly have unspecified other impact via crafted system calls.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2017-15951 resides within the Linux kernel's KEYS subsystem, specifically affecting versions prior to 4.13.10. This issue represents a critical race condition that undermines the integrity of key management operations within the kernel's security framework. The KEYS subsystem serves as a fundamental component for managing cryptographic keys and credentials across the operating system, making this vulnerability particularly concerning for system security and stability. The flaw manifests when the kernel fails to properly synchronize concurrent operations involving key updates and key lookups, creating a window where malicious or crafted system calls can exploit this timing vulnerability to compromise system functionality.
The technical implementation of this race condition occurs within the negative key state handling mechanism of the KEYS subsystem. When a key is in the negative state, it represents a key that has been marked as not existing or has failed to be found during lookup operations. The vulnerability arises because the kernel does not adequately protect against simultaneous access patterns where one thread attempts to update a key while another attempts to find or access the same key in its negative state. This synchronization failure allows for unpredictable behavior during concurrent key operations, potentially leading to memory corruption or system instability. The race condition specifically affects the atomicity of key state transitions and can be triggered through carefully crafted system calls that manipulate key management functions.
From an operational perspective, this vulnerability presents significant risks to system availability and potentially confidentiality. Local attackers with access to the system can leverage this race condition to cause denial of service attacks by triggering system crashes or lockups through carefully constructed key management operations. The unspecified other impacts mentioned in the vulnerability description suggest potential for privilege escalation or information disclosure, though the exact scope of these additional consequences requires further analysis. The vulnerability's local nature means it cannot be exploited remotely, but it represents a serious threat to systems where local access is possible, particularly in multi-user environments or containerized deployments where privilege boundaries may be compromised.
The mitigation strategy for CVE-2017-15951 involves immediate kernel version upgrades to 4.13.10 or later, which contain the necessary synchronization fixes for the KEYS subsystem race condition. System administrators should prioritize patching all affected systems, particularly those running older kernel versions or custom kernel builds that may not have received the specific fix. Additionally, organizations should implement monitoring for unusual key management activity patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-362, which describes race conditions in concurrent programming, and may relate to ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities. Organizations should also consider implementing kernel hardening measures such as enabling stack canaries and other memory protection mechanisms to reduce the overall attack surface and potential impact of similar vulnerabilities in the future.