CVE-2017-15299 in Linux
Summary
by MITRE
The KEYS subsystem in the Linux kernel through 4.13.7 mishandles use of add_key for a key that already exists but is uninstantiated, which allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact via a crafted system call.
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Analysis
by VulDB Data Team • 01/03/2023
The vulnerability identified as CVE-2017-15299 resides within the Linux kernel's KEYS subsystem, specifically affecting versions through 4.13.7. This flaw represents a critical design oversight in how the kernel handles key management operations, particularly when attempting to add keys that already exist but remain uninstantiated. The KEYS subsystem serves as a fundamental component for managing cryptographic keys and credentials across the Linux operating system, making this vulnerability particularly concerning from a security perspective. The vulnerability stems from inadequate validation mechanisms within the kernel's key management code, where the system fails to properly handle edge cases involving duplicate key entries that have not yet been fully initialized.
The technical implementation of this vulnerability involves a NULL pointer dereference condition that occurs during the add_key system call execution. When a local user attempts to add a key that already exists within the kernel's keyring but has not yet been instantiated, the kernel's internal state management becomes inconsistent. This inconsistency leads to a scenario where the system attempts to dereference a NULL pointer, resulting in an immediate system crash and complete denial of service. The underlying issue manifests in the kernel's inability to properly distinguish between valid and invalid key addition attempts, particularly when dealing with keys that exist in a transitional state between creation and instantiation. This flaw operates at the kernel level, making it particularly dangerous as it can be exploited by any local user with minimal privileges, effectively bypassing traditional user permission boundaries.
The operational impact of CVE-2017-15299 extends beyond simple system crashes, representing a potential vector for more sophisticated attacks. While the primary effect is a denial of service condition that can bring systems to their knees, the vulnerability could potentially be leveraged to escalate privileges or create additional attack vectors. The vulnerability's classification aligns with CWE-476, which addresses NULL pointer dereference conditions in software systems, and demonstrates how kernel-level flaws can create cascading security issues. From an attacker's perspective, this vulnerability represents a low-hanging fruit that can be exploited to disrupt services without requiring elevated privileges, making it particularly attractive for malicious actors seeking to cause system instability or perform reconnaissance activities. The vulnerability's exploitation can result in complete system unavailability, potentially leading to significant business disruption and data loss incidents.
Mitigation strategies for this vulnerability require immediate kernel updates to versions that address the underlying design flaw in the KEYS subsystem. System administrators should prioritize patching affected systems to prevent exploitation, as the vulnerability can be triggered through simple system calls without requiring special privileges. Additionally, implementing monitoring solutions that can detect unusual patterns in key management operations may help identify potential exploitation attempts. The vulnerability's impact on system stability necessitates comprehensive testing of patched kernels to ensure that the fix does not introduce regressions in key management functionality. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of local privilege escalation attempts, though the primary defense remains the timely application of kernel security patches. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the kernel's credential management subsystem as a means to gain system control.