CVE-2024-40933 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
iio: temperature: mlx90635: Fix ERR_PTR dereference in mlx90635_probe()
When devm_regmap_init_i2c() fails, regmap_ee could be error pointer, instead of checking for IS_ERR(regmap_ee), regmap is checked which looks like a copy paste error.
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Analysis
by VulDB Data Team • 08/10/2025
The vulnerability CVE-2024-40933 represents a critical error handling flaw in the Linux kernel's industrial I/O subsystem, specifically within the mlx90635 temperature sensor driver. This issue resides in the device probe function where improper error checking leads to potential system instability. The mlx90635 driver is designed to interface with infrared temperature sensors commonly used in industrial automation and embedded systems, making this vulnerability particularly concerning for mission-critical applications. The flaw demonstrates a classic programming error that can result in kernel panics or system crashes when hardware initialization fails.
The technical root cause stems from a copy-paste error in the mlx90635_probe() function where the code incorrectly checks for errors in the regmap variable rather than the intended regmap_ee variable. When devm_regmap_init_i2c() fails during device initialization, it returns an error pointer instead of a valid regmap structure. The original code fails to properly validate whether regmap_ee contains an error pointer before proceeding with operations on it, creating a scenario where ERR_PTR dereference occurs. This type of error handling mistake falls under the category of improper error checking and validation, which is a well-documented weakness in software security practices. The flaw directly violates proper kernel programming practices and can lead to undefined behavior when the kernel attempts to dereference an error pointer as if it were a valid memory address.
The operational impact of this vulnerability extends beyond simple system crashes, affecting the reliability of industrial systems that depend on accurate temperature monitoring. When the mlx90635 driver fails to properly handle initialization errors, it can cause entire kernel subsystems to become unstable, potentially leading to data corruption, service disruption, or complete system failure. This is particularly problematic in environments where temperature monitoring is critical for process control, safety systems, or automated manufacturing processes. The vulnerability affects systems running Linux kernels with the affected IIO subsystem, making it relevant to a broad range of embedded devices, industrial controllers, and IoT platforms that utilize this specific temperature sensor driver. Organizations deploying systems with this driver face potential operational risks that could result in costly downtime or safety hazards.
Mitigation strategies for CVE-2024-40933 involve applying the official kernel patch that corrects the error checking logic in the mlx90635_probe() function. System administrators should prioritize updating their kernel versions to include the fix, which is typically available through standard distribution channels and security updates. The patch ensures that IS_ERR() is properly applied to regmap_ee instead of the incorrect regmap variable, preventing the dereference of error pointers. Organizations should also implement monitoring to detect potential system instability that might occur during the transition period before full patch deployment. Regular kernel security audits and vulnerability assessments are recommended to identify similar issues in other device drivers. Additionally, system administrators should consider implementing proper error handling mechanisms and ensuring that all kernel components undergo rigorous testing before deployment in production environments. This vulnerability aligns with CWE-476 which describes null pointer dereference, and could potentially be leveraged in privilege escalation scenarios if exploited in kernel space, making it a significant concern for system security.