CVE-2026-74552 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (lm90) Only report alarms if driver is ready
Userspace can read sysfs attributes before driver registration is complete, immediately after devm_hwmon_device_register_with_info() has been called. At that time, data->hwmon_dev is not yet initialized. This can trigger a NULL pointer access since lm90_update_device() and with it lm90_update_alarms_locked() will be called. This call schedules report_work and lm90_report_alarms(), which passes the still-NULL data->hwmon_dev to hwmon_notify_event() and triggers a NULL pointer dereference.
Fix the problem by only scheduling the report and alert workers data->hwmon_dev is set.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability in question affects the Linux kernel's hardware monitoring subsystem, specifically the lm90 driver responsible for managing temperature sensors. This issue represents a classic race condition scenario where userspace applications can access sysfs attributes before the driver initialization process has fully completed. The problem manifests when devm_hwmon_device_register_with_info() is invoked but the data->hwmon_dev field remains uninitialized, creating a window of opportunity for null pointer dereference attacks.
The technical flaw stems from improper synchronization between driver registration and userspace attribute access. When lm90_update_device() is called during early initialization, it triggers lm90_update_alarms_locked() which subsequently schedules report_work and lm90_report_alarms(). These functions attempt to pass the uninitialized data->hwmon_dev pointer to hwmon_notify_event(), resulting in a NULL pointer dereference that can crash the kernel or provide attackers with potential privilege escalation vectors. This vulnerability aligns with CWE-476 which addresses null pointer dereference conditions, and represents a classic example of inadequate initialization checking before function calls.
The operational impact of this vulnerability extends beyond simple kernel crashes to potentially enable privilege escalation attacks within the system's hardware monitoring framework. Attackers could exploit this timing window to force kernel memory corruption or execute arbitrary code with kernel privileges, particularly when combined with other exploitation techniques targeting the same race condition window. The vulnerability affects systems using lm90 hardware monitoring drivers and impacts the broader hwmon subsystem, making it a critical issue for server and embedded systems that rely on hardware monitoring capabilities.
Mitigation strategies should focus on implementing proper initialization checks before scheduling work queues and ensuring that all required data structures are fully initialized before allowing userspace access. The fix involves modifying the driver to only schedule report and alert workers once data->hwmon_dev is properly set, preventing premature execution of functions that depend on complete driver initialization. This approach aligns with ATT&CK technique T1068 which covers local privilege escalation through kernel vulnerabilities, and follows best practices for avoiding race conditions in kernel development as outlined in the Linux kernel security documentation. The solution demonstrates proper defensive programming principles by ensuring data integrity before function execution, preventing unauthorized access to uninitialized memory structures.