CVE-2026-93199 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
i3c: master: Do not treat master device as a duplicate target
i3c_master_search_i3c_dev_duplicate() searches the bus for another I3C device with the same PID as the reference device. The search can match master->this, causing the controller itself to be returned as a duplicate.
Since the controller is not a target device, it cannot be a duplicate of one. Exclude master->this from matching so that the function only returns real duplicate target devices.
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Analysis
by VulDB Data Team • 09/18/2026
The Inter-Integrated Circuit (I3C) bus standard defines a dynamic address assignment mechanism where slave devices are assigned unique identifiers known as Persistent Unique Identifiers or PIDs during the enumeration phase. This process is critical for establishing communication topology on the bus, ensuring that each device can be addressed individually without conflict. The Linux kernel implements this functionality through specific driver subsystems within the i3c master controller code. A logical flaw was identified in the function responsible for detecting duplicate devices, specifically i3c_master_search_i3c_dev_duplicate(). This routine is designed to scan the bus topology to identify if any existing device shares a PID with a newly discovered or referenced device, which would indicate a configuration error or hardware fault requiring resolution before communication can proceed safely.
The technical vulnerability stems from an incorrect boundary condition in the duplicate detection algorithm. When searching for devices that share the same PID as a reference target, the iteration logic inadvertently included the master controller itself, represented internally by master->this, within the set of potential matches. Since the I3C specification dictates that only slave devices possess PIDs and participate in address assignment negotiations, the host controller or master device does not have a valid PID for comparison purposes. Consequently, including the master entity in this search creates a logical inconsistency where the system incorrectly interprets its own presence as a duplicate target entry on the bus.
This flaw results in false positive detection of duplicate devices. When the kernel erroneously identifies the master controller as a conflicting device with the same PID as an actual slave, it may trigger error handling routines intended for genuine conflicts. This can lead to unnecessary failure states during I3C initialization or re-enumeration processes, potentially causing the bus driver to abort operations, fail to bind devices, or report spurious errors to higher-level system components. Such behavior degrades system reliability and complicates debugging efforts by masking actual hardware issues with software-induced logic errors that stem from improper entity classification within the enumeration loop.
From a security and stability perspective, this issue aligns with CWE-841 Improper Enforcement of Behavioral Workflow because the code fails to correctly enforce the distinction between master and slave entities during protocol execution. It also relates to CWE-20 Improper Input Validation insofar as the input data (the list of devices on the bus) is not filtered against expected entity types before processing. In terms of MITRE ATT&CK, while this is primarily a reliability issue rather than an exploit vector for unauthorized access, it falls under T1564 Hidden Elements if one considers how such logic errors can obscure true system state during forensic analysis or automated monitoring tools that rely on accurate bus topology reporting.
To mitigate this vulnerability and ensure robust operation of the I3C subsystem, developers must modify the duplicate search function to explicitly exclude the master device from the iteration scope. By filtering out master->this before comparing PIDs, the algorithm ensures that only actual slave devices are evaluated for duplication conflicts. This correction restores logical integrity to the enumeration process, preventing false positives and ensuring that genuine PID collisions are accurately reported while normal bus operations proceed without interruption due to spurious conflict detections.