CVE-2026-80861 usb: xhci: bail out of setup if the controller is inaccessible
A kernel oops occurs when the xHCI USB controller is inaccessible, causing a denial of service on Linux systems with affected hardware.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80861?
CVE-2026-80861 is a vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-80861?
How do I fix CVE-2026-80861?
Apply the vendor's patch.
Is CVE-2026-80861 being exploited?
There is no known exploitation of CVE-2026-80861 in the wild and no public exploit code.
Sources
Also known as AZL-99639, BELL-CVE-2026-80861, DEBIAN-CVE-2026-80861, GHSA-8wxp-3ggp-2gcw, UBUNTU-CVE-2026-80861.