CVE-2026-98262

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

ata: libahci: clear PxCLBU and PxFBU for AHCI_HFLAG_32BIT_ONLY

A user reported that commit 105c42566a55 ("ata: ahci: force 32-bit DMA for

JMicron JMB582/JMB585") made the JMicron JMB585 unusable on his board.

The failure is seen as soon as the ahci driver is probed, and booting with

iommu=off does not solve the problem.

Looking at the AHCI specification, PxCLBU and PxFBU are both read only '0'

for HBAs that do not support 64-bit addressing.

For HBAs that do support 64-bit addressing, the registers are read write,

with a reset value that is Implementation Specific.

When using the AHCI_HFLAG_32BIT_ONLY flag, the HBA does support 64-bit

addressing, and a 32-bit DMA mask is set by simply clearing HOST_CAP_64.

Thus, in this case, we need to explicitly clear the registers to 0.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References