CVE-2026-98658: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-98658 is a buffer overflow flaw in the Linux kernel's IIO proximity driver that affects firmware parsing validation. Attackers could exploit truncated firmware images to read beyond buffer boundaries. This article covers technical details, affected versions, impact assessment, and mitigation strategies.

CVE-2026-98658 Overview

CVE-2026-98658 affects the Linux kernel iio proximity driver for the AW96103 sensor. The firmware parser reads a length value from the binary header and uses it to walk six-byte register/value entries. A truncated firmware image can cause the parser to read beyond the copied firmware buffer. A header value smaller than the four-byte count field underflows, producing an excessively large length. The fix validates the header size, rejects underflowed lengths, and ensures the computed payload fits within the firmware image.

Critical Impact
A malformed firmware image loaded by the aw96103 driver can trigger an out-of-bounds read in kernel memory, leading to information disclosure or kernel instability.

Affected Products

Linux kernel versions containing the drivers/iio/proximity/aw96103 firmware parser prior to the fix
Stable kernel branches referenced by commits 1a7c522, 4a9b9f2, 6501b03, and 815ae0b
Systems using the AW96103 proximity sensor with vendor-supplied firmware blobs

Discovery Timeline

2026-10-18 - CVE-2026-98658 published to NVD
2026-10-19 - Last updated in NVD database

Technical Details for CVE-2026-98658

Vulnerability Analysis

The flaw resides in the AW96103 proximity sensor firmware loader within the Linux kernel's Industrial I/O (iio) subsystem. The parser consumes a length field from the firmware binary header and iterates over six-byte register/value tuples using that length. Two conditions produce memory safety issues. First, a truncated firmware blob with a declared length larger than the actual buffer causes the parser to read past the end of the allocated firmware buffer. Second, a length value smaller than the four-byte count field underflows during arithmetic, producing a very large unsigned length that drives iteration far beyond legitimate bounds. Both conditions result in an out-of-bounds read [CWE-125] in kernel address space.

Root Cause

The parser trusts the length field without validating header size, without checking for arithmetic underflow, and without ensuring the derived payload size fits inside the firmware image or divides evenly into six-byte entries. The field was also read without using get_unaligned_le32(), exposing additional endian and alignment risks on affected architectures.

Attack Vector

Exploitation requires loading a crafted firmware image through the kernel firmware loading mechanism used by the aw96103 driver. In practice this requires local privileges sufficient to supply or replace the firmware file in the firmware search path, or a supply-chain scenario where a malicious firmware blob reaches the device. The vulnerability is not network-reachable. No public exploit is available, and the EPSS score indicates low probability of exploitation activity.

No verified proof-of-concept code is available. Technical details are documented in the upstream fix commits linked in Kernel Git Commit 815ae0b.

Detection Methods for CVE-2026-98658

Indicators of Compromise

Kernel log entries from the aw96103 driver reporting firmware parsing errors, truncated firmware, or unexpected register writes
Unexpected aw96103 firmware files in /lib/firmware/ with modified timestamps or non-vendor hashes
Kernel oops or KASAN out-of-bounds read reports referencing the aw96103 firmware parser

Detection Strategies

Audit the integrity of firmware blobs under /lib/firmware/ using cryptographic hashes against vendor-provided references
Enable CONFIG_KASAN on test kernels to surface out-of-bounds reads during driver load and firmware updates
Review package manager logs for installation of unsigned or out-of-policy firmware packages

Monitoring Recommendations

Forward kernel ring buffer (dmesg) and journald logs to a central telemetry pipeline for anomaly review
Alert on kernel subsystem crashes or driver initialization failures involving iio proximity components
Track running kernel versions across the fleet to confirm patched builds are deployed on affected hardware

How to Mitigate CVE-2026-98658

Immediate Actions Required

Apply the upstream fix commits 1a7c522, 4a9b9f2, 6501b03, and 815ae0b or install a distribution kernel that includes them
Restrict write access to /lib/firmware/ to root and trusted package management processes only
Verify that only vendor-signed aw96103 firmware images are present on affected systems

Patch Information

The fix reads the little-endian length field with get_unaligned_le32(), validates the header size, rejects underflowed lengths, confirms the payload is contained within the firmware image, and requires the payload to consist of whole six-byte register/value entries. Patched commits are available at Kernel Git Commit 1a7c522, Kernel Git Commit 4a9b9f2, Kernel Git Commit 6501b03, and Kernel Git Commit 815ae0b.

Workarounds

Blacklist the aw96103 kernel module on systems that do not require AW96103 proximity sensor functionality
Remove unused aw96103 firmware files from /lib/firmware/ to prevent the driver from loading untrusted blobs
Enforce secure boot and signed kernel module policies to reduce exposure to malicious firmware delivery

bash

# Blacklist the aw96103 driver until a patched kernel is deployed
echo 'blacklist aw96103' | sudo tee /etc/modprobe.d/blacklist-aw96103.conf
sudo update-initramfs -u