CVE-2026-64376 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
firmware_loader: fix device reference leak in firmware_upload_register()
firmware_upload_register() -> fw_create_instance() -> device_initialize()
After fw_create_instance() succeeds, the lifetime of the embedded struct device is expected to be managed through the device core reference counting, since fw_create_instance() has already called device_initialize().
In firmware_upload_register(), if alloc_lookup_fw_priv() fails after fw_create_instance() succeeds, the code reaches free_fw_sysfs and frees fw_sysfs directly instead of releasing the device reference with put_device(). This may leave the reference count of the embedded struct device unbalanced, resulting in a refcount leak.
The issue was identified by a static analysis tool I developed and confirmed by manual review. Fix this by using put_device(fw_dev) in the failure path and letting fw_dev_release() handle the final cleanup, instead of freeing the instance directly from the error path.
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Analysis
by VulDB Data Team • 07/26/2026
The vulnerability resides within the linux kernel's firmware loading subsystem where a reference count leak occurs during firmware upload registration. This issue specifically affects the firmware_loader component and manifests when firmware_upload_register() function encounters a failure condition after successfully executing fw_create_instance(). The flaw creates a scenario where device reference counting becomes unbalanced due to improper cleanup handling in error paths.
The technical implementation of this vulnerability stems from the improper management of embedded struct device references within the firmware loading framework. When firmware_upload_register() calls fw_create_instance(), it initializes the device structure through device_initialize() which establishes proper reference counting mechanisms. However, subsequent failure conditions in alloc_lookup_fw_priv() after fw_create_instance() succeeds do not properly release the device reference using put_device(). Instead, the code directly invokes free_fw_sysfs() which bypasses the standard device core reference management, leaving the embedded struct device with an inflated reference count.
This memory management error creates a persistent reference leak that can accumulate over time and potentially lead to system instability or resource exhaustion. The vulnerability represents a classic improper resource handling issue where cleanup paths do not mirror initialization sequences, violating fundamental software engineering principles for resource management. The static analysis tool used to identify this flaw demonstrates how automated code analysis can detect subtle reference counting errors in complex kernel subsystems.
The operational impact of this vulnerability extends beyond simple memory leaks as it affects the reliability and stability of firmware loading operations across linux systems. System administrators may observe gradual degradation in performance or unexpected behavior when firmware upload registration fails repeatedly, since each failure leaves behind unreleased device references that can eventually consume system resources. The vulnerability affects all systems utilizing the linux kernel's firmware loader functionality, particularly those implementing custom firmware upload mechanisms.
The fix for this vulnerability involves modifying the error handling path in firmware_upload_register() to properly release device references using put_device(fw_dev) instead of direct memory freeing operations. This ensures that the embedded struct device reference count is properly decremented and managed through the standard device core subsystem rather than bypassing it entirely. The corrected implementation allows fw_dev_release() to handle final cleanup operations, maintaining consistency between initialization and termination sequences. This approach aligns with established kernel development practices and follows proper resource management protocols that prevent reference counting anomalies.
This vulnerability type corresponds to CWE-404, which addresses improper resource release or unbalanced resource management, and relates to ATT&CK technique T1547.006 for privilege escalation through kernel module manipulation. The fix demonstrates proper adherence to kernel subsystem design principles where device references must always be balanced through corresponding increment and decrement operations, ensuring system stability and preventing potential denial-of-service conditions that could arise from accumulated reference leaks.