CVE-2026-23092: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-23092 Overview

CVE-2026-23092 is an out-of-bounds write vulnerability discovered in the Linux kernel's IIO (Industrial I/O) subsystem, specifically within the ad3552r-hs DAC (Digital-to-Analog Converter) driver. The flaw exists in the ad3552r_hs_write_data_source function where improper handling of buffer indexing can lead to stack-based memory corruption.

When simple_write_to_buffer() succeeds, it returns the number of bytes actually copied to the buffer. However, the vulnerable code incorrectly uses the count parameter as the index for null termination instead of the actual bytes copied. If the count exceeds the 64-byte stack buffer size, the code performs buf[count] = '\0', causing an out-of-bounds write on the stack.

Critical Impact

Local attackers with access to the device node can trigger stack buffer overflow by writing more than 64 bytes, potentially leading to kernel memory corruption, denial of service, or privilege escalation.

Affected Products

• Linux kernel with IIO subsystem enabled
• Systems using the ad3552r-hs DAC driver
• Linux kernel versions prior to the security patch

Discovery Timeline

• February 4, 2026 - CVE-2026-23092 published to NVD
• February 5, 2026 - Last updated in NVD database

Technical Details for CVE-2026-23092

Vulnerability Analysis

This vulnerability represents a classic boundary condition error in kernel driver code. The ad3552r_hs_write_data_source function allocates a fixed 64-byte stack buffer to receive user-supplied data through the simple_write_to_buffer() kernel helper function. The fundamental issue lies in the disconnect between the user-supplied count parameter and the actual number of bytes written to the buffer.

The function fails to account for the scenario where count exceeds the allocated buffer size. While simple_write_to_buffer() correctly limits the actual copy operation to the buffer boundaries, the subsequent null termination operation directly uses the unchecked count value as an array index, bypassing the protection afforded by the copy function.

This vulnerability was identified through static analysis and shares similarities with the issue addressed in kernel commit da9374819eb3 ("iio: backend: fix out-of-bound write"), indicating a recurring pattern in IIO subsystem code.

Root Cause

The root cause is improper input validation combined with incorrect index usage for array access. The code path trusts the user-supplied count parameter for determining the null terminator position without validating that it falls within the bounds of the 64-byte stack buffer. The return value from simple_write_to_buffer(), which indicates the actual bytes copied and is bounded by the buffer size, should have been used as the index for null termination instead.

Attack Vector

The attack requires local access to the system with the ability to open and write to the affected device node. An attacker can exploit this vulnerability by:

1. Opening the vulnerable device node associated with the ad3552r-hs driver
2. Writing more than 64 bytes of data to the device
3. The oversized write triggers the out-of-bounds stack buffer write

The vulnerability was validated using a demo module under QEMU, where writing 128 bytes of arbitrary data to the device node causes an overflow of the 64-byte stack buffer. KASAN (Kernel Address Sanitizer) detects and reports the out-of-bounds access during exploitation attempts.

Since no verified code examples are available, the vulnerability mechanism can be understood conceptually: a 64-byte stack buffer receives data, but the null termination index is determined by user-controlled input rather than the bounded return value, allowing writes beyond the allocated memory region.

Detection Methods for CVE-2026-23092

Indicators of Compromise

• KASAN reports indicating out-of-bounds write operations in the IIO subsystem
• Kernel panic or crash logs referencing ad3552r_hs_write_data_source function
• Unexpected system instability when interacting with IIO DAC devices
• Memory corruption artifacts in kernel space near IIO driver operations

Detection Strategies

• Enable KASAN (Kernel Address Sanitizer) to detect out-of-bounds memory access attempts
• Monitor kernel logs for IIO subsystem errors or stack corruption indicators
• Deploy runtime kernel exploit detection tools that monitor for stack buffer overflows
• Use audit logging to track access to IIO device nodes

Monitoring Recommendations

• Implement system call monitoring for unusual write operations to device nodes
• Configure kernel logging to capture IIO subsystem debug information
• Deploy endpoint detection solutions capable of identifying kernel memory corruption attempts
• Establish baseline metrics for IIO driver operations to detect anomalous behavior

How to Mitigate CVE-2026-23092

Immediate Actions Required

• Apply the official kernel patches immediately on affected systems
• Restrict access to IIO device nodes to trusted users only
• Enable KASAN on development and staging systems to detect exploitation attempts
• Monitor systems for signs of exploitation while patches are being deployed

Patch Information

The Linux kernel maintainers have released patches to address this vulnerability. The fix involves adding a proper bounds check for the count parameter and using the return value from simple_write_to_buffer() as the index for null termination instead of the user-supplied count.

The patches are available through the official kernel git repositories:

• Kernel Git Commit 978d28136c53
• Kernel Git Commit db16e7c52032

Workarounds

• Restrict access permissions to the affected IIO device nodes using appropriate file system permissions
• Disable the ad3552r-hs driver module if the hardware is not required for system operation
• Implement mandatory access control policies (SELinux/AppArmor) to limit device node access
• Consider unloading the vulnerable kernel module until patching is possible

# Restrict access to IIO device nodes
chmod 600 /sys/bus/iio/devices/*/data_source
chown root:root /sys/bus/iio/devices/*/data_source

# Disable the vulnerable module if not needed
modprobe -r ad3552r-hs
echo "blacklist ad3552r-hs" >> /etc/modprobe.d/blacklist.conf