CVE-2026-80861
Received Received - Intake

Unaligned Memory Access in Linux Kernel XHCI Driver

Publication date: 2026-09-04

Last updated on: 2026-09-04

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: usb: xhci: bail out of setup if the controller is inaccessible xhci_gen_setup() locates the operational registers using the capability length read from the very first register: xhci->op_regs = hcd->regs + HC_LENGTH(readl(&xhci->cap_regs->hc_capbase)); If the controller is dead or has dropped off the bus, that read returns ~0, HC_LENGTH() truncates it to 0xff, and op_regs ends up 0xff bytes past the page-aligned MMIO base, i.e. unaligned. The first access through it, xhci_halt() -> xhci_handshake() reading op_regs->status, is then an unaligned readl() on device memory. arm64 faults on unaligned device accesses, so instead of xhci_handshake() catching the all-ones value and returning -ENODEV, setup oopses: xhci-pci-renesas 0005:08:00.0: Unable to change power state from D3cold to D0, device inaccessible xhci-pci-renesas 0005:08:00.0: xHCI Host Controller xhci-pci-renesas 0005:08:00.0: new USB bus registered, assigned bus number 1 Unable to handle kernel paging request at virtual address ffff80030a770103 ESR = 0x0000000096000021 FSC = 0x21: alignment fault Internal error: Oops: 0000000096000021 [#1] SMP pc : xhci_halt [xhci_hcd] Call trace: xhci_halt xhci_gen_setup xhci_pci_setup usb_add_hcd usb_hcd_pci_probe xhci_pci_common_probe xhci_pci_renesas_probe This was hit with a Renesas uPD720201 that failed to power up ("Unable to change power state from D3cold to D0, device inaccessible") yet still reached the HCD probe path. Read the capability register once, and if it reads back the all-ones value (as xhci_handshake() and xhci_reset() already test for), abort setup with -ENODEV before op_regs is derived from it. Reading it once also avoids re-reading a register that may change under a concurrent hot-removal.

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Meta Information

Published
2026-09-04
Last Modified
2026-09-04
Generated
2026-09-04
AI Q&A
2026-09-04
EPSS Evaluated
N/A
NVD
CVE-2026-80861
EUVD
EUVD-2026-71311

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel occurs when the xHCI controller is inaccessible or dead. The setup process incorrectly calculates the operational register location due to a read returning all-ones (~0), leading to an unaligned memory access. This causes an alignment fault on arm64 systems, resulting in a kernel panic or crash.

Detection Guidance

This vulnerability is specific to the Linux kernel's xHCI USB controller handling. Detection requires checking kernel logs for unaligned memory access errors or xHCI controller initialization failures. Monitor dmesg for messages like 'Unable to handle kernel paging request' or 'xHCI Host Controller' errors. Check if Renesas uPD720201 controllers fail to power up with 'Unable to change power state from D3cold to D0'.

Impact Analysis

If your system uses a Renesas uPD720201 or similar xHCI controller that fails to power up, this vulnerability could cause the system to crash during USB initialization. This may lead to data loss, service disruption, or require a reboot to recover.

Mitigation Strategies

Apply the latest Linux kernel update that includes the fix for this issue. If immediate patching is not possible, disable the affected xHCI controller or USB devices using it. Monitor vendor advisories for Renesas uPD720201 firmware updates. Ensure proper power management settings for USB controllers.

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