CVE-2026-63934: Linux Kernel Information Disclosure Flaw

CVE-2026-63934 Overview

CVE-2026-63934 is a Linux kernel vulnerability in the iio/gyro/itg3200 driver. The function itg3200_read_all_channels() incorrectly passes the address of its local pointer parameter to i2c_transfer() instead of the caller's scan buffer. The result is that gyroscope sample data is written to a discarded stack slot, while uninitialized stack contents are pushed to userspace through /dev/iio:deviceX on every scan. The defect is both a functional bug and an information leak from kernel stack memory to unprivileged consumers of the triggered buffer interface.

Critical Impact
Uninitialized kernel stack memory is leaked to userspace via the IIO triggered buffer on every gyroscope scan, exposing potentially sensitive kernel data.

Affected Products

Linux kernel iio/gyro/itg3200 driver (InvenSense ITG-3200 gyroscope)
Multiple stable Linux kernel branches receiving backported fixes
Systems exposing the IIO triggered buffer interface via /dev/iio:deviceX

Discovery Timeline

2026-07-19 - CVE-2026-63934 published to NVD
2026-07-19 - Last updated in NVD database

Technical Details for CVE-2026-63934

Vulnerability Analysis

The defect is a pointer-address mistake in itg3200_read_all_channels(). The function receives __be16 *buf as a parameter and constructs an i2c_msg with the destination expressed as (char *)&buf. Because buf is a pointer parameter, &buf yields the address of the local pointer variable on the stack, not the caller's buffer. The (char *) cast silences the type mismatch that would otherwise be caught by the compiler.

When i2c_transfer() runs, it writes ITG3200_SCAN_ELEMENTS * sizeof(s16) (8 bytes) into that local stack slot. The bytes are discarded when the function returns. The caller in itg3200_trigger_handler() never receives sensor data, and iio_push_to_buffers_with_timestamp() forwards whatever uninitialized stack contents happen to reside in the caller's scan buffer to userspace.

The non-buffered read_raw() path is unaffected. It routes through itg3200_read_reg_s16(), which uses &out on a local s16 variable where taking the address is correct. This aligns with an uninitialized memory use pattern combined with kernel information disclosure.

Root Cause

The root cause is a misuse of the address-of operator on a pointer parameter combined with an explicit cast that hides the resulting type mismatch. The intent was to pass buf (the caller's buffer) to i2c_transfer(); the implementation passed &buf (the address of the local pointer slot). The fix is to drop the spurious & so the I2C read populates the caller's scan buffer.

Attack Vector

A local user with read access to /dev/iio:deviceX for a system exposing an ITG-3200 gyroscope through the triggered buffer interface can read uninitialized kernel stack contents. The leak occurs on every scan, so repeated reads can accumulate stack bytes across many kernel call sites. No special privileges beyond IIO device access are required, and no exploit code is needed beyond opening the device and reading samples.

See the upstream fix in the Linux Kernel Commit 15a0b3f and additional stable backports including Commit 31bbd4b, Commit 63203bd, and Commit cfc3283.

Detection Methods for CVE-2026-63934

Indicators of Compromise

No network indicators exist for this issue; exploitation is local and read-only.
Anomalous or nonsensical gyroscope readings from ITG-3200 devices via the triggered buffer are a functional symptom of the defect.
Processes with unexpected open file descriptors on /dev/iio:deviceX when no legitimate sensor consumer is deployed.

Detection Strategies

Inventory kernel versions across Linux fleets and flag hosts running unpatched kernels that build the itg3200 driver (CONFIG_ITG3200=y or module).
Audit which processes open /dev/iio:device* character devices, correlating against expected sensor daemons.
Verify sample integrity by comparing values from read_raw sysfs attributes against the triggered buffer output; large divergence signals the bug.

Monitoring Recommendations

Log open() calls on /dev/iio:device* using auditd or eBPF tooling and alert on non-baseline consumers.
Track kernel package inventory in the endpoint telemetry pipeline to identify hosts still exposing the vulnerable driver.
Monitor for unusual read volume against IIO character devices, which can indicate scraping of leaked stack bytes.

How to Mitigate CVE-2026-63934

Immediate Actions Required

Apply the upstream fix that removes the spurious & in itg3200_read_all_channels() or upgrade to a stable kernel that includes one of the referenced backports.
Restrict access to /dev/iio:device* to trusted service accounts through udev rules and filesystem permissions.
Unload the itg3200 module on systems that do not use the sensor: modprobe -r itg3200.

Patch Information

The fix is available across multiple stable branches. Reference commits include 15a0b3f, 31bbd4b, 63203bd, 6bdc30, 8654b5e, 90e8093, b64dd5f, and cfc3283. Rebuild kernels from a fixed stable tag and redeploy, then reboot affected hosts.

Workarounds

Blocklist the itg3200 module in /etc/modprobe.d/ on systems that do not require the sensor.
Set strict permissions on /dev/iio:device* via udev rules so only a dedicated sensor group can read the interface.
Avoid using the triggered buffer path for the ITG-3200 until patched; consumers can fall back to the unaffected read_raw sysfs attributes.

bash

# Blocklist the vulnerable driver on hosts that do not need it
echo 'blacklist itg3200' | sudo tee /etc/modprobe.d/blacklist-itg3200.conf
sudo modprobe -r itg3200 2>/dev/null || true

# Restrict IIO character device access to a trusted group
cat <<'EOF' | sudo tee /etc/udev/rules.d/90-iio-restrict.rules
KERNEL=="iio:device*", GROUP="iiousers", MODE="0640"
EOF
sudo udevadm control --reload-rules && sudo udevadm trigger