CVE-2026-98759 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
usb: typec: tipd: fix uninitialized typec_partner_desc in cd321x_update_work()
cd321x_update_work() passes a stack-allocated typec_partner_desc to typec_register_partner() after initializing only usb_pd, accessory and identity.
typec_register_partner() copies attach and deattach from the descriptor into the partner. With those fields left unset, garbage function pointers may be stored and later invoked from typec_partner_link_device() when a USB device is linked to the port. Uninitialized pd_revision and usb_capability similarly leak stack data through partner sysfs.
Zero-initialize the descriptor so optional callbacks remain NULL and the remaining fields are zero.
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Analysis
by VulDB Data Team • 10/18/2026
The vulnerability identified in the Linux kernel's Type-C Port Controller Driver for Texas Instruments devices, specifically within the cd321x_update_work function, represents a critical memory safety issue stemming from improper initialization of stack-allocated data structures. The core technical flaw lies in the partial initialization of a typec_partner_desc structure before it is passed to the typec_register_partner() routine. While specific fields such as usb_pd, accessory, and identity are explicitly set by the driver logic, other critical members within the descriptor remain uninitialized. In C programming, stack-allocated variables that are not fully initialized retain whatever data previously existed in those memory locations on the kernel stack. This behavior creates a scenario where sensitive or arbitrary data from previous function calls remains present in the unused portions of the structure, leading to potential information disclosure and code execution risks depending on how these uninitialized fields are interpreted by subsequent system components.
The operational impact of this flaw is twofold, involving both security vulnerabilities related to memory safety and functional integrity issues within the USB Type-C subsystem. First, when typec_register_partner() processes the descriptor, it copies function pointers such as attach and detach into the partner object. Because these fields were not explicitly set to NULL in the cd321x_update_work routine, they contain garbage values derived from stack memory. If these garbage values are interpreted as valid function pointers by the kernel's device linking mechanisms, specifically within typec_partner_link_device(), it can lead to a crash or arbitrary code execution when the system attempts to invoke them during USB device attachment events. This constitutes an invalid pointer dereference vulnerability that compromises system stability and security. Second, uninitialized fields such as pd_revision and usb_capability result in the leakage of kernel stack data through partner sysfs interfaces. Attackers with local access can read these sysfs entries to extract sensitive information from the kernel memory space, which may include pointers, cryptographic keys, or other confidential data used by prior operations on that specific CPU core's stack.
From a classification perspective, this vulnerability aligns with CWE-457, which describes the use of an uninitialized variable, and specifically touches upon CWE-908 regarding the use of uninitialized variables in security-critical contexts. The potential for executing arbitrary code via corrupted function pointers maps to ATT&CK technique T1203, Exploitation for Client Execution, if leveraged through a physical USB connection attack vector. Furthermore, the information leakage aspect corresponds to CWE-200, Exposure of Sensitive Information to an Unauthorized Actor. These classifications highlight that while the root cause is simple memory management negligence, the resulting threat model includes both privilege escalation via code execution and confidentiality breaches via data exfiltration through standard system interfaces.
The resolution implemented in this patch addresses the issue by enforcing zero-initialization of the typec_partner_desc structure before any fields are populated. By using a method such as memset or designated initializers to set all bytes of the descriptor to zero, the driver ensures that optional callback pointers like attach and detach remain NULL rather than containing garbage data. Similarly, numeric fields like pd_revision and usb_capability are explicitly cleared, preventing stack data leakage through sysfs. This approach adheres to secure coding standards by assuming no trust in uninitialized memory states. For system administrators and developers, this fix underscores the importance of rigorous initialization practices in kernel drivers that interact with hardware interfaces. Mitigation strategies include applying the latest kernel updates provided by distribution vendors or upstream maintainers. Additionally, static analysis tools should be employed during development to detect partial initializations of complex structures passed into registration functions, ensuring that all members are either explicitly set or zeroed out before use.