CVE-2023-6535 in Linux
Summary
by MITRE • 02/07/2024
A flaw was found in the Linux kernel's NVMe driver. This issue may allow an unauthenticated malicious actor to send a set of crafted TCP packages when using NVMe over TCP, leading the NVMe driver to a NULL pointer dereference in the NVMe driver, causing kernel panic and a denial of service.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/02/2025
The vulnerability identified as CVE-2023-6535 represents a critical flaw within the Linux kernel's NVMe over TCP implementation that exposes systems to remote denial of service attacks. This issue specifically affects the NVMe driver's handling of crafted TCP packets, creating a pathway for malicious actors to exploit the kernel's memory management mechanisms. The vulnerability resides in the network transport layer implementation of the NVMe protocol when operating over TCP connections, making it particularly concerning for enterprise storage environments that rely heavily on NVMe over TCP for high-performance data access.
The technical root cause of this vulnerability stems from insufficient input validation within the NVMe driver's TCP packet processing routines. When the driver receives malformed or specially crafted TCP packets, it fails to properly validate the packet structure before attempting to dereference pointers within the packet data. This leads to a NULL pointer dereference condition that crashes the kernel's NVMe subsystem and ultimately results in a complete system kernel panic. The flaw demonstrates characteristics consistent with CWE-476_NULL_pointer_dereference, where the driver code does not adequately check for null values before accessing memory locations. The vulnerability is classified as a remote code execution risk due to its ability to be triggered over the network without authentication requirements, making it particularly dangerous in connected environments.
The operational impact of CVE-2023-6535 extends beyond simple service disruption, as it can affect entire storage subsystems and potentially compromise system availability in mission-critical environments. Organizations utilizing NVMe over TCP for storage area networks, cloud infrastructure, or high-performance computing clusters face significant risk from this vulnerability. The denial of service condition can persist until system reboot occurs, potentially leading to extended downtime for applications that depend on NVMe storage access. Attackers can leverage this vulnerability to target storage servers, SAN switches, or any system implementing NVMe over TCP protocols, making it a particularly attractive vector for disruptive attacks. The vulnerability's exploitation requires minimal privileges and can be executed remotely, aligning with ATT&CK technique T1499.004 for network denial of service attacks.
Mitigation strategies for CVE-2023-6535 should prioritize immediate patching of affected Linux kernel versions, as vendors have released security updates addressing the NULL pointer dereference issue. System administrators should implement network segmentation and access controls to limit exposure of NVMe over TCP endpoints to trusted networks only. Monitoring for unusual TCP packet patterns and implementing intrusion detection systems can help identify potential exploitation attempts. Organizations should also consider disabling NVMe over TCP functionality if it is not essential for operations, as this removes the attack surface entirely. The vulnerability highlights the importance of proper input validation in kernel space drivers and demonstrates why security testing of network protocols is crucial for maintaining system integrity. Regular security assessments of storage subsystems and network protocols should be conducted to identify similar vulnerabilities in other kernel modules or network implementations.