CVE-2026-31389 in Linux
Summary
by MITRE • 04/03/2026
In the Linux kernel, the following vulnerability has been resolved:
spi: fix use-after-free on controller registration failure
Make sure to deregister from driver core also in the unlikely event that per-cpu statistics allocation fails during controller registration to avoid use-after-free (of driver resources) and unclocked register accesses.
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Analysis
by VulDB Data Team • 05/20/2026
The vulnerability identified as CVE-2026-31389 represents a critical use-after-free condition within the Linux kernel's SPI (Serial Peripheral Interface) subsystem that occurs during controller registration failure scenarios. This flaw specifically manifests when the kernel attempts to register an SPI controller but encounters a failure during per-cpu statistics allocation, creating a dangerous state where driver resources become prematurely freed while still being referenced. The issue resides in the kernel's device driver core mechanisms that manage controller registration and resource cleanup, where inadequate error handling leads to inconsistent state management between the driver subsystem and the underlying hardware abstraction layers.
The technical root cause of this vulnerability stems from improper resource management during the SPI controller registration process, particularly when memory allocation for per-cpu statistics fails. When the kernel allocates resources for controller registration, it follows a sequence where controller structures are initialized, statistics are allocated, and the controller is registered with the driver core. However, if per-cpu statistics allocation fails after initial controller structure setup but before successful registration, the cleanup process fails to properly deregister the controller from the driver core subsystem. This creates a scenario where the controller structure may be freed from memory while references to it still exist within the driver core's internal data structures, leading to use-after-free conditions that can be exploited by malicious actors to execute arbitrary code or cause system crashes.
This vulnerability directly maps to CWE-416, which describes the use of freed memory condition, and aligns with ATT&CK technique T1059.001 for command and script injection through kernel-level exploits. The operational impact of this vulnerability extends beyond simple system instability, as it creates potential attack vectors that could be leveraged for privilege escalation or denial-of-service attacks. When an attacker can trigger the specific failure condition during controller registration, they may be able to manipulate the kernel's memory management to execute arbitrary code with kernel-level privileges. The unclocked register accesses mentioned in the description indicate that the vulnerability could also lead to memory corruption in adjacent kernel structures, potentially compromising the integrity of the entire kernel memory space.
The mitigation strategy for this vulnerability requires careful attention to proper resource cleanup and error handling within the kernel's driver core subsystem. The fix implemented in the resolution ensures that when per-cpu statistics allocation fails during controller registration, the system properly deregisters the controller from the driver core even in these unlikely failure scenarios. This approach prevents the use-after-free condition by maintaining consistent state management between the allocation subsystem and the driver core's registration mechanisms. System administrators should prioritize applying the kernel patches that address this specific vulnerability, particularly in environments where SPI controllers are actively used or where the system may be exposed to untrusted input that could trigger the problematic registration path. The fix demonstrates the importance of comprehensive error handling in kernel code and highlights the need for proper resource management even in edge cases that are considered unlikely but can still occur in production environments.