CVE-2026-53400 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
i2c: core: fix adapter registration race
Adapters can be looked up based on their id using i2c_get_adapter() which takes a reference to the embedded struct device.
Make sure that the adapter (including its struct device) has been initialised before adding it to the IDR to avoid accessing uninitialised data which could, for example, lead to NULL-pointer dereferences or use-after-free.
Note that the i2c-dev chardev, which is registered from a bus notifier, currently uses i2c_get_adapter() so the adapter needs to be added to the IDR before registration.
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Analysis
by VulDB Data Team • 07/19/2026
This vulnerability resides within the Linux kernel's I2C subsystem where a race condition exists during adapter registration that can lead to critical system instability. The issue manifests when adapters are registered and subsequently looked up by their identifier using the i2c_get_adapter() function, which is designed to retrieve a reference to the embedded struct device associated with each adapter. The core problem occurs because the adapter structure including its device component may not be fully initialized before being added to the Internal Dynamic Reclamation (IDR) data structure used for identifier-based lookups.
The technical flaw stems from improper synchronization during the adapter registration lifecycle where the kernel fails to ensure complete initialization of adapter structures before making them available through the IDR lookup mechanism. This creates a window where concurrent threads or processes attempting to access newly registered adapters via i2c_get_adapter() may encounter uninitialized memory segments, potentially resulting in NULL-pointer dereferences or use-after-free conditions that can crash the kernel or provide attack vectors for privilege escalation.
The operational impact of this vulnerability extends beyond simple system crashes as it affects the fundamental I2C bus infrastructure that many hardware components depend upon. Since i2c-dev character device registration occurs through a bus notifier mechanism and relies on i2c_get_adapter() for lookup operations, any race condition during this process can compromise the entire I2C subsystem's stability. This vulnerability particularly affects systems with multiple concurrent I2C adapter registrations or high-frequency bus activity where timing variations increase the probability of encountering the race condition.
The mitigation strategy requires ensuring proper initialization ordering before adding adapters to the IDR structure, typically implemented through synchronization mechanisms such as mutexes or spinlocks to prevent concurrent access during critical initialization phases. This approach aligns with common security practices for preventing race conditions in kernel space operations and addresses the underlying CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) vulnerability pattern. The fix essentially implements proper ordering semantics that guarantee adapter structures are fully constructed and validated before becoming accessible through the i2c_get_adapter() interface, thereby preventing unauthorized access to uninitialized memory regions and maintaining system stability during concurrent I2C operations. This vulnerability demonstrates how seemingly minor synchronization issues in kernel subsystems can have significant security implications when not properly addressed through defensive programming practices that ensure proper resource lifecycle management.