CVE-2026-63908 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
Input: atmel_mxt_ts - fix boundary check in mxt_prepare_cfg_mem
When a configuration file provides an object size that is larger than the driver's known mxt_obj_size(object), the driver intends to discard the extra bytes.
The loop iterates using for (i = 0; i < size; i++). Inside the loop, the condition to skip processing extra bytes is:
if (i > mxt_obj_size(object)) continue;
Since i is a 0-based index, the valid indices for the object are 0 through mxt_obj_size(object) - 1.
When i == mxt_obj_size(object), the condition evaluates to false, and the code processes the byte instead of discarding it.
This causes the code to calculate byte_offset = reg + i - cfg->start_ofs and writes the byte there, overwriting exactly one byte of the adjacent instance or object.
Update the boundary check to skip extra bytes correctly by using >=.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability in the atmel_mxt_ts driver represents a critical boundary checking flaw that could lead to memory corruption and potential privilege escalation within the Linux kernel. This issue affects the mxt_prepare_cfg_mem function where configuration data is processed for touchscreen controllers, specifically targeting how the driver handles object size validation during configuration file parsing. The flaw stems from an improper comparison operator in a loop condition that controls byte processing, creating a scenario where one extra byte beyond the expected object size gets incorrectly written to memory. The vulnerability manifests when a configuration file contains an object with a size parameter larger than what the driver expects, causing the boundary check to fail and resulting in unintended memory overwrites.
The technical implementation of this flaw involves a fundamental error in conditional logic within a for loop that processes configuration data bytes. When iterating through configuration data with the loop structure for (i = 0; i < size; i++), the driver employs an incorrect boundary condition that fails to account for zero-based indexing properly. The original condition if (i > mxt_obj_size(object)) continue; creates a logical error because it allows processing of the byte at index mxt_obj_size(object) rather than skipping it. This misalignment occurs due to the comparison operator being greater than instead of greater than or equal to, which means that when i equals the object size, the condition evaluates to false and execution continues instead of skipping. This subtle but critical error results in a single byte being written to memory location that should be protected from configuration data modification, effectively overwriting adjacent memory regions.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially compromise system integrity and security. When an attacker can manipulate configuration files or inject malicious data through legitimate means such as firmware updates or device configuration processes, they gain the capability to overwrite critical memory locations within the kernel's touchscreen driver context. This type of memory corruption could lead to system instability, denial of service conditions, or even enable privilege escalation attacks that allow unauthorized code execution in kernel space. The vulnerability affects systems running Linux kernels with the atmel_mxt_ts touchscreen driver, particularly those handling device configuration through external sources, making it relevant for embedded systems, IoT devices, and mobile platforms where such drivers are commonly deployed.
The fix implemented addresses this boundary checking error by modifying the comparison operator from > to >=, ensuring that when i equals mxt_obj_size(object), the loop correctly skips processing of that byte instead of allowing it to be written to memory. This change aligns with proper defensive programming practices and follows established security principles for buffer overflow prevention. The solution represents a straightforward but critical correction that maintains the intended behavior of discarding extra bytes while preventing accidental overwrites of adjacent memory regions. From a cybersecurity perspective, this vulnerability demonstrates the importance of careful boundary condition implementation in kernel drivers, where even minor logical errors can create significant security implications. The fix should be applied across all affected Linux kernel versions and distributions to ensure comprehensive protection against this specific class of memory corruption vulnerabilities.
This vulnerability aligns with CWE-129: Improper Validation of Array Index and CWE-787: Out-of-bounds Write, both of which are classified as high-risk security issues in the Common Weakness Enumeration catalog. The flaw also relates to ATT&CK technique T1068: Exploitation for Privilege Escalation, as memory corruption vulnerabilities in kernel drivers can be leveraged to gain elevated privileges and control over system operations. The atmel_mxt_ts driver vulnerability exemplifies how seemingly minor implementation details in device driver code can create significant security risks, particularly when dealing with configuration data processing that involves boundary validation and memory management operations within kernel space contexts.