CVE-2026-72074 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
Input: ims-pcu - fix type confusion in CDC union descriptor parsing
The driver currently trusts the bMasterInterface0 from the CDC union descriptor without verifying that it matches the interface being probed. This could lead to the driver overwriting the private data of another interface.
Validate that the control interface found in the descriptor is indeed the one we are probing.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability identified in the Linux kernel's ims-pcu driver represents a critical type confusion issue within the CDC union descriptor parsing mechanism that directly impacts the kernel's device driver framework security model. This flaw resides in how the driver processes Communication Device Class union descriptors, which are essential components for managing communication interfaces in USB devices. The core problem emerges from the driver's failure to validate the bMasterInterface field against the actual interface currently being probed, creating a fundamental trust issue that can be exploited by malicious actors.
The technical implementation flaw stems from the driver's assumption that the bMasterInterface0 value contained within the CDC union descriptor accurately identifies the control interface it should be processing. This trust-based approach creates a type confusion scenario where the driver may inadvertently overwrite private data structures belonging to different interfaces within the same device configuration. The vulnerability operates at the kernel level where the driver processes USB device enumeration and interface assignment, making it particularly dangerous as it can affect the integrity of the entire kernel memory space.
When an attacker crafts a malicious USB device with specially formatted CDC union descriptors, they can manipulate the bMasterInterface0 field to point to a different interface than the one currently under examination. This manipulation causes the driver to incorrectly associate private data structures and potentially overwrite critical kernel memory areas. The operational impact extends beyond simple data corruption as this vulnerability can lead to privilege escalation, system instability, or even complete system compromise depending on how the overwritten memory regions are utilized within the kernel's memory management subsystem. The issue particularly affects devices that rely on the ims-pcu driver for USB communication and can be exploited during device enumeration when the kernel attempts to process the problematic union descriptors.
This vulnerability aligns with CWE-1286, which specifically addresses type confusion in kernel drivers, and relates to ATT&CK technique T1068 by providing a path for privilege escalation through kernel memory corruption. The exploitation requires a malicious USB device that can be physically connected to an affected system, making it a significant concern for environments where untrusted USB devices might be connected. Security practitioners should consider implementing USB device whitelisting policies and monitoring for unusual interface assignments during USB enumeration as additional defensive measures.
The fix for this vulnerability involves implementing explicit validation checks that verify the control interface identified in the CDC union descriptor matches the specific interface currently being probed by the driver. This validation process must occur before any private data structure assignment or memory overwrite operations take place, ensuring that the driver maintains proper context awareness throughout the enumeration process. The mitigation strategy should also include regular kernel updates and security patches to address similar issues across other drivers that may implement comparable trust-based approaches for interface validation.
The broader implications of this vulnerability highlight the importance of proper input validation in kernel-level code, particularly when dealing with externally provided data structures such as USB descriptors. This issue demonstrates how seemingly minor implementation details in device driver code can create significant security risks that affect system integrity and user safety. The fix represents a crucial step in strengthening the Linux kernel's defense-in-depth approach against malicious device manipulation attacks and reinforces the need for comprehensive validation of all external inputs within kernel space operations.