CVE-2026-98201

A flaw was found in the Linux kernel's input subsystem. When handling 32-bit compatibility requests for force feedback input effects, the kernel fails to properly initialize memory buffers before copying data from user space. A local user can exploit this vulnerability to read uninitialized kernel stack data, leading to information disclosure of potentially sensitive system memory.

A kernel stack information disclosure occurs in input_ff_effect_from_user() because the 32-bit compat path copies only struct ff_effect_compat into a larger native struct ff_effect. The remaining bytes retain previous kernel stack contents and input_ff_upload() stores the complete native structure in the force feedback effect table. A uinput based force feedback daemon can later receive these bytes through UI_BEGIN_FF_UPLOAD. For the CVSS the PR:L value is used because a local user or process must access the relevant input device and trigger the compat force feedback upload path. The base score uses AC:H and C:L because exploitation depends on a 32-bit compat caller, a suitable force feedback device, and a cooperating uinput based daemon, while the directly exposed data is limited to the uninitialized structure tail. The paranoid score uses AC:L and C:H when this environment is already available because repeated kernel stack disclosures may expose addresses or other sensitive values and can weaken protections such as KASLR. The issue is not network reachable. It does not provide a direct write primitive or a demonstrated standalone privilege escalation path, but the disclosed kernel data may assist exploitation of another vulnerability.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.