CVE-2026-68353: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-68353 Overview

CVE-2026-68353 is an out-of-bounds read vulnerability in the Linux kernel ath6kl Wi-Fi driver. The flaw resides in the ath6kl_wmi_tx_complete_event_rx() function, which processes WMI (Wireless Module Interface) TX completion events from firmware. The firmware-controlled num_msg field, an unsigned 8-bit integer, drives a loop without validation against the actual buffer length. A malicious or compromised firmware can supply an inflated num_msg value, causing the kernel to read up to 1020 bytes past the WMI event buffer.

Critical Impact
An attacker with control over the Wi-Fi firmware or a co-located adjacent-network attacker can trigger kernel memory disclosure and disrupt the wireless subsystem on affected Linux systems.

Affected Products

Linux kernel versions containing the ath6kl Wi-Fi driver prior to the patch commits
Systems using Qualcomm Atheros AR6003/AR6004 Wi-Fi chipsets bound to the ath6kl driver
Embedded and IoT Linux distributions shipping vulnerable kernel builds

Discovery Timeline

2026-08-10 - CVE-2026-68353 published to NVD
2026-08-13 - Last updated in NVD database

Technical Details for CVE-2026-68353

Vulnerability Analysis

The vulnerability is an out-of-bounds read [CWE-125] in the ath6kl Wi-Fi driver's WMI event handling path. When the driver receives a TX completion event from firmware, ath6kl_wmi_tx_complete_event_rx() iterates num_msg times over variable-length entries following a fixed event header. Because num_msg is untrusted firmware-supplied data with a range of 0-255, an inflated value causes the loop to read memory beyond the allocated WMI event buffer.

Each iteration reads a per-message structure, and with num_msg set to 255, the resulting overread can reach up to 1020 bytes past the buffer boundary. This exposes adjacent kernel heap contents, which may contain sensitive data such as pointers, credentials, or cryptographic material. The overread can also trigger crashes if the read crosses into unmapped memory, producing a denial-of-service condition.

Root Cause

The root cause is missing input validation on firmware-controlled data. The driver trusts the num_msg field without verifying that the WMI event buffer is large enough to contain the fixed header plus num_msg variable-length entries. The fix adds a length check to ensure the buffer holds the expected number of entries before the loop executes.

Attack Vector

Exploitation requires either compromised Wi-Fi firmware or an adjacent-network attacker capable of influencing WMI event content reaching the host driver. Because the attack surface is adjacent (AV:A), the attacker must be within radio range or on the same logical wireless network segment. No authentication or user interaction is required to trigger the flawed code path once a malicious WMI event is delivered.

The vulnerability is described in prose only; verified proof-of-concept code is not publicly available. See the upstream commits linked in the Kernel Git Commit 289edc3 and Kernel Git Commit eb636fb for the exact code changes.

Detection Methods for CVE-2026-68353

Indicators of Compromise

Unexpected kernel warnings or KASAN reports referencing ath6kl_wmi_tx_complete_event_rx in dmesg or system logs
Kernel oops or panic entries citing the ath6kl module during Wi-Fi activity
Repeated Wi-Fi interface resets or firmware reloads on systems using AR6003/AR6004 chipsets

Detection Strategies

Enable Kernel Address Sanitizer (KASAN) on test builds to surface out-of-bounds reads in the ath6kl driver path
Monitor kernel ring buffer output for module tainting or crash traces originating from wireless drivers
Inventory endpoints running the ath6kl driver using lsmod or modinfo telemetry and correlate against installed kernel versions

Monitoring Recommendations

Ingest kernel and dmesg logs into a centralized SIEM or data lake for cross-fleet correlation of ath6kl faults
Alert on abnormal frequencies of Wi-Fi driver reload events, which can indicate exploitation attempts against embedded devices
Track kernel package versions across the Linux estate and flag hosts running kernels that predate the fix commits

How to Mitigate CVE-2026-68353

Immediate Actions Required

Upgrade to a Linux kernel release that includes one of the fix commits: 289edc3c7134, 3a21c89215cc, 69ac7ba3a3df, c38b0d5c6619, or eb636fbc4431
Apply distribution vendor kernel updates as soon as they become available for stable, long-term-support, and hardware-enablement kernels
Prioritize patching on embedded and IoT devices using Qualcomm Atheros AR6003/AR6004 chipsets, which are common in older mobile and single-board hardware

Patch Information

The upstream fix adds a bounds check ensuring the WMI event buffer is large enough to hold the fixed structure and the num_msg variable-length entries before iterating. The patch has been backported across multiple stable branches. Reference commits: Kernel Git Commit 289edc3, Kernel Git Commit 3a21c89, Kernel Git Commit 69ac7ba, Kernel Git Commit c38b0d5, and Kernel Git Commit eb636fb.

Workarounds

Unload the ath6kl module on systems that do not require the affected Wi-Fi hardware using modprobe -r ath6kl_sdio or modprobe -r ath6kl_usb
Blacklist the driver via /etc/modprobe.d/ on devices where wireless functionality is not needed
Restrict physical and radio proximity access to devices using vulnerable AR6003/AR6004 chipsets until patched

bash

# Blacklist the ath6kl driver until patched
echo "blacklist ath6kl_sdio" | sudo tee /etc/modprobe.d/ath6kl-cve-2026-68353.conf
echo "blacklist ath6kl_usb" | sudo tee -a /etc/modprobe.d/ath6kl-cve-2026-68353.conf
sudo modprobe -r ath6kl_sdio ath6kl_usb ath6kl_core 2>/dev/null
sudo update-initramfs -u