CVE-2026-74276

What the bug is

The method the driver uses to determine the size of the FIFO has a problem. What it currently does is this: It stops the SPI hardware and writes to the TX FIFO register until TX FIFO FULL asserts in the status register. But the hardware does not only have the FIFO, it also has a shift register which can hold a byte. This can be seen, when writing a byte to the FIFO (while the SPI hardware is stopped,) the TX FIFO EMPTY is still empty. So, if we have a FIFO size of 16 for example, the current method returns a 17. This is a problem, at least when using the driver in irq mode. The same size determined for the TX FIFO is also assumed for the RX FIFO. When a SPI transaction wants to write the amount of the FIFO size or more bytes, the following happens, for example with 16 bytes FIFO size: The driver stops the SPI hardware and writes 17 bytes to the TX FIFO and starts the SPI hardware and goes sleep. The hardware then shifts out 17 bytes (FIFO + shift register) and simultaneously reads bytes into the RX FIFO, but it only has 16 places, so it looses one byte. Then TX FIFO empty asserts, wakes the driver again, which has a fast path and reads 16 bytes from the RX FIFO, but before reading the last 17th byte (which is lost) it does this: sr = xspi->read_fn(xspi->regs + XSPI_SR_OFFSET); if (!(sr & XSPI_SR_RX_EMPTY_MASK)) { xilinx_spi_rx(xspi); rx_words--; } It reads the status register and checks if the RX FIFO is not empty. But it is empty in our case. So this check spins in a while loop forever locking the driver. This patch fixes the logic to determine the FIFO size.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/spi/spi-xilinx.c

What this is

SPI SUBSYSTEMMAINTAINERS section matched on drivers/spi/ · linux-spi@vger.kernel.org · Maintained

Kernel module

none to look for. The file would have gone into spi_xilinx, and Debian does not compile it into that module, so finding spi_xilinx in lsmod would say nothing about this CVE.

Check it on the machine

grep -wE 'CONFIG_SPI|CONFIG_SPI_XILINX' /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

Show whether Debian builds this, per release

Debian does not build this code. In 4 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.

• bookworm, trixie, forky, sidn

n

not enabled on any flavour - this release does not build the code

Build switches

CONFIG_SPI, CONFIG_SPI_XILINX

Reads as

all on means the file is compiled; any one off means it is not.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-08-15 (2 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.18%, higher than 6.8% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/spi

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
4.0	5.10.261	4ee65558a7fd
4.0	5.15.212	e98f589d5406
4.0	6.1.178	1fc6a6c0cc77
4.0	6.6.145	dfab0d4698a6
4.0	6.12.97	d7ccd8736b67
4.0	6.18.40	1c9246a199e1
4.0	7.1.5	d1944b71c18e
4.0	7.2	47f3b5365536