CVE-2026-80566
Received Received - Intake

Buffer Overflow in Hynitron CSTxxx Touchscreen Driver

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: Input: hynitron_cstxxx - validate touch count and finger IDs The driver allocates max_touch_num input slots, which are indexed from zero through max_touch_num - 1. The current check allows a finger ID equal to max_touch_num to reach cst3xx_report_contact(). While the input core ignores out-of-range slot indices, reporting touch data without a valid slot change corrupts the touch state of the previously active slot. The touch count is read from the controller's report and is used to index the fixed-size report buffer without first checking its range. Reject counts larger than the supported number of touch slots before checking the trailing byte or parsing touch data. Reject finger IDs equal to or greater than max_touch_num, and return immediately when an invalid finger ID is encountered so that corrupt touch frames are discarded instead of reporting partial contact state. The V821 Avaota F1 board configures the vendor driver with one touch slot, so finger ID 1 is already invalid on that device.

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Meta Information

Published
2026-08-26
Last Modified
2026-08-26
Generated
2026-08-26
AI Q&A
2026-08-26
EPSS Evaluated
N/A
NVD
CVE-2026-80566
EUVD
EUVD-2026-66481

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
hynitron hynitron_cstxxx *

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability is in the Linux kernel's hynitron_cstxxx driver, which handles touch input. The driver allocates a fixed number of touch slots but incorrectly allows finger IDs equal to or exceeding the maximum slot count. This causes the driver to report corrupted touch data, potentially corrupting the state of previously active touch slots.

Detection Guidance

This vulnerability affects the Linux kernel's hynitron_cstxxx driver for touchscreen devices. Detection requires checking if the vulnerable driver is loaded and inspecting kernel logs for touch-related errors or crashes. Commands like 'lsmod | grep hynitron_cstxxx' can verify if the driver is loaded. Check kernel logs with 'dmesg | grep cstxxx' for errors indicating invalid touch counts or finger IDs.

Impact Analysis

This vulnerability could cause touch input to malfunction, such as incorrect touch detection or unresponsive touchscreen behavior. On devices like the V821 Avaota F1 board, it may lead to complete failure of touch input since finger ID 1 is invalid.

Mitigation Strategies

Immediate mitigation involves updating the Linux kernel to a patched version that resolves this issue. If updating is not immediately possible, disable the hynitron_cstxxx driver by blacklisting it using 'echo 'blacklist hynitron_cstxxx' >> /etc/modprobe.d/blacklist.conf' followed by 'update-initramfs -u' and rebooting.

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