Bug 2524461 (CVE-2026-80566)

Summary: CVE-2026-80566 kernel: Input: hynitron_cstxxx - validate touch count and finger IDs
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the `hynitron_cstxxx` driver in the Linux kernel. This vulnerability allows an attacker to provide specially crafted touch input that can bypass validation checks for touch count and finger identifiers (IDs). This improper handling can lead to the corruption of the touch state or the discarding of valid touch frames, effectively causing a denial of service for the touch input functionality.
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Description OSIDB Bzimport 2026-08-26 14:57:18 UTC 
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.
Comment 1 gkamathe 2026-08-27 09:28:12 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082611-CVE-2026-80566-0da4@gregkh/T