CVE-2026-72128 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
nvmet: fix refcount leak in nvmet_sq_create()
In nvmet_sq_create(), a reference on the ctrl is taken via kref_get_unless_zero() before calling nvmet_check_sqid(). If nvmet_check_sqid() fails, the function returns the error directly without releasing the reference, leading to a leak.
Fix this by jumping to the "ctrl_put" label, which already performs the necessary nvmet_ctrl_put(ctrl). This ensures the reference is properly released on this error path.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability resides in the Linux kernel's nvme target subsystem where the nvmet_sq_create() function exhibits a reference count leak during error handling scenarios. This issue specifically impacts the NVMe over Fabrics target implementation which serves as a critical component for storage networking infrastructure. The flaw manifests when the function attempts to acquire a reference on the controller structure using kref_get_unless_zero() before proceeding with nvmet_check_sqid() validation. When this validation fails, the function returns an error code without properly releasing the previously acquired reference, creating a memory leak that can accumulate over time.
The technical root cause stems from improper error path handling within the nvmet_sq_create() function which follows an incorrect control flow pattern. The kref_get_unless_zero() call successfully increments the reference count on the controller structure, but subsequent failure in nvmet_check_sqid() does not execute the proper cleanup routine that would decrement this reference. This pattern violates standard resource management practices and creates a persistent leak that can eventually lead to system instability or resource exhaustion. The vulnerability directly relates to CWE-404 which defines improper resource release or reclaim, specifically targeting reference counting mechanisms in kernel space.
The operational impact of this vulnerability extends beyond simple memory consumption as it affects the reliability and stability of NVMe target implementations across various storage environments. Systems utilizing NVMe over Fabrics target functionality may experience progressive memory degradation, particularly under high load conditions where multiple queue creation attempts occur. The leak can compound over time, potentially leading to system crashes or degraded performance in storage subsystems that rely heavily on NVMe target services. This represents a significant concern for enterprise storage infrastructure where continuous operation and resource efficiency are paramount.
The fix implements a controlled error handling path that redirects execution to an existing cleanup label named "ctrl_put" which already contains the necessary nvmet_ctrl_put(ctrl) call. This approach ensures that regardless of whether nvmet_check_sqid() succeeds or fails, the reference counting mechanism operates correctly through established cleanup routines. The solution leverages existing infrastructure rather than introducing new code paths, maintaining consistency with established kernel patterns and reducing the risk of introducing additional vulnerabilities. This remediation aligns with ATT&CK technique T1490 which focuses on resource exhaustion attacks, by preventing the specific memory leak that could contribute to such conditions.
The vulnerability demonstrates a classic example of improper error handling in kernel space operations where resource management is critical for system stability. The fix represents a defensive programming approach that ensures all code paths properly release acquired resources, following the principle of "acquire early, release late" in kernel development practices. This type of reference counting error is particularly dangerous in kernel modules as it can lead to cascading failures throughout the system's memory management subsystem. The resolution maintains backward compatibility while strengthening the overall robustness of the NVMe target implementation against resource exhaustion scenarios that could be exploited by malicious actors or occur naturally through system stress conditions.
This vulnerability and its fix highlight the importance of rigorous testing for error paths in kernel code, particularly around reference counting operations that are fundamental to Linux kernel object lifecycle management. The issue showcases how seemingly minor oversight in control flow can lead to significant resource management problems in production systems. Proper implementation of such fixes ensures that storage infrastructure maintains predictable performance characteristics and prevents potential denial of service conditions that could impact data availability for critical enterprise applications relying on NVMe over Fabrics protocols.