---
id: "CVE-2026-98711"
kind: "vulnerability"
aliases: ["CVE-2026-98711"]
title: "Linux kernel: cw1200 Wi-Fi driver leaks heap bytes to its device"
severity: "low"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["cw1200", "embedded", "linux-kernel", "package", "wifi"]
not_affected_if: ["driver-not-loaded", "no-cw1200-hardware"]
published_at: "2026-10-18T16:17:24+00:00"
first_seen_at: "2026-10-23T21:57:16+00:00"
updated_at: "2026-10-25T05:17:32+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98711", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel: cw1200 Wi-Fi driver leaks heap bytes to its device

The cw1200 Wi-Fi driver in the Linux kernel pads outgoing SDIO or SPI transfers past the end of the frame buffer, so up to 511 bytes of kernel heap memory per frame are sent to the wireless chip. The exposure is to the device itself, which a hostile or compromised wireless module could collect.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check whether the cw1200 driver is loaded with `lsmod | grep cw1200` or whether `cw1200_wlan_sdio` or `cw1200_wlan_spi` modules exist for your kernel.
- Compare the running kernel with the fixed release listed in the kernel stable tree commit for this CVE (unknown from the sources).

## Fix

- Update the Linux kernel to a release that includes the upstream commit fixing cw1200 TX padding (exact fixed version: unknown from the sources).
- If the cw1200 hardware is not used, blacklist the module, for example `echo 'blacklist cw1200_wlan_sdio' > /etc/modprobe.d/cw1200.conf`.

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98711

## From the sources

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

wifi: cw1200: fix TX padding OOB read leaking heap data to device

The TX path rounds the transfer size up to the bus alignment
(align_size(), up to 511 bytes for SDIO, 1 byte for SPI) but sends
the padded length straight from the frame buffer, which has no room
reserved for the padding.  cw1200_data_write() therefore reads past
the end of the frame and the bus transfer carries those bytes to the
device.  A bogus device can collect up to 511 bytes of kernel heap
data per TX frame.

The RX path does not have this problem: it allocates the skb with
the aligned length (alloc_len) before reading.

Compute the exact padding with the bus align_size() callback, make
sure queued TX frames have tailroom for it, and zero the padding
bytes before the transfer so nothing past the frame is exposed.

This is not expected to change driver behavior on most cases: frame
contents and transfer sizes are unchanged, only the content of the
padding bytes (previously undefined stale memory, now zero), which
the device never reads since the WSM header carries the real frame
length.  The skb expansion can only fail under memory exhaustion,
in which case the frame is dropped like on the existing error paths
of cw1200_tx().

Discovered by Atuin - Automated Vulnerability Discovery Engine.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_