CVE-2026-23062: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-23062 Overview

A vulnerability has been discovered in the Linux kernel's hp-bioscfg driver that causes a kernel panic when accessing sysfs attributes. The flaw exists in the GET_INSTANCE_ID macro, which contains both an off-by-one error leading to out-of-bounds array access and a missing NULL check that causes a null pointer dereference.

When userspace tools such as fwupd attempt to read BIOS configuration attributes via sysfs, the vulnerable code path is triggered, resulting in a general protection fault and subsequent kernel panic. The vulnerability specifically affects the min_length_show() function and other attribute show functions in the hp_bioscfg module.

Critical Impact

This vulnerability can cause system crashes (kernel panic) when legitimate firmware management tools interact with HP BIOS configuration interfaces, leading to denial of service conditions on affected systems.

Affected Products

• Linux kernel with hp-bioscfg driver (platform/x86: hp-bioscfg module)
• HP systems utilizing the BIOS configuration sysfs interface
• Systems running fwupd or similar firmware management utilities on affected kernels

Discovery Timeline

• 2026-02-04 - CVE CVE-2026-23062 published to NVD
• 2026-02-05 - Last updated in NVD database

Technical Details for CVE-2026-23062

Vulnerability Analysis

The vulnerability consists of two distinct memory safety issues within the GET_INSTANCE_ID macro in the hp-bioscfg driver. This driver provides a sysfs interface for managing HP BIOS configuration settings from userspace.

The first issue is an off-by-one error in the loop boundary condition. The loop used <= instead of < for comparison against instances_count, causing the code to access memory beyond the bounds of the array. Since array indices in C are 0-based (ranging from 0 to instances_count-1), using <= causes an access to index instances_count, which is outside the valid range.

The second issue is a missing NULL pointer validation. Before dereferencing attr_name_kobj->name, the code failed to verify that attr_name_kobj was not NULL. This results in a null pointer dereference when the kernel object structure is not properly initialized or has been freed.

The kernel panic manifests when tools like fwupd attempt to read BIOS configuration attributes through the sysfs interface:

Oops: general protection fault [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
RIP: 0010:min_length_show+0xcf/0x1d0 [hp_bioscfg]

Root Cause

The root cause is improper boundary checking and insufficient input validation in the GET_INSTANCE_ID macro. The off-by-one error (<= vs <) is a common programming mistake that leads to buffer over-read conditions. Combined with the missing NULL check for attr_name_kobj, these issues create a reliable crash condition when the sysfs attributes are accessed.

The pattern of correct loop bounds exists elsewhere in the driver, suggesting this was an oversight during the implementation of the GET_INSTANCE_ID macro.

Attack Vector

The vulnerability is triggered through local access to the sysfs interface. An attacker with local access to the system could intentionally trigger the kernel panic by reading specific sysfs attributes exposed by the hp-bioscfg driver. However, the more common trigger scenario involves legitimate firmware management tools like fwupd that automatically read BIOS configuration attributes during normal operation.

The exploitation path is as follows: a user or automated process reads from the sysfs attributes (e.g., via /sys/class/firmware-attributes/), which invokes attribute show functions like min_length_show(). The vulnerable GET_INSTANCE_ID macro is executed, causing either an out-of-bounds memory access or a null pointer dereference, resulting in a kernel panic and system crash.

Detection Methods for CVE-2026-23062

Indicators of Compromise

• Kernel panic messages referencing hp_bioscfg module in system logs
• General protection fault errors with KASAN: null-ptr-deref signatures
• Stack traces showing min_length_show or similar attribute show functions from the hp_bioscfg module
• Unexpected system reboots on HP systems when fwupd or similar tools are running

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for general protection faults associated with the hp_bioscfg module
• Implement alerts for kernel panics with RIP addresses pointing to hp_bioscfg module functions
• Review system stability logs for repeated crashes correlated with firmware management tool execution
• Use kernel address sanitizer (KASAN) reports to identify null pointer dereference patterns

Monitoring Recommendations

• Enable kernel crash dump collection (kdump) to capture detailed diagnostic information on affected systems
• Configure automatic monitoring for kernel oops messages containing hp_bioscfg signatures
• Track system uptime anomalies on HP systems running firmware management software
• Implement proactive scanning for vulnerable kernel versions on HP hardware deployments

How to Mitigate CVE-2026-23062

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the fix for CVE-2026-23062
• If immediate patching is not possible, consider unloading the hp_bioscfg module using modprobe -r hp_bioscfg
• Disable or postpone automatic firmware management tool execution until systems are patched
• Review system stability and ensure crash dump collection is enabled for diagnostic purposes

Patch Information

Multiple kernel patches have been released to address this vulnerability. The fix adds a NULL check for attr_name_kobj before dereferencing and corrects the loop boundary condition to use < instead of <=, matching the pattern used elsewhere in the driver.

The following patch commits are available:

• Linux Kernel Patch - 193922a23d72
• Linux Kernel Patch - 25150715e0b0
• Linux Kernel Patch - eb5ff1025c92
• Linux Kernel Patch - eba49c1dee9c

Workarounds

• Unload the hp_bioscfg kernel module if HP BIOS configuration via sysfs is not required
• Blacklist the module to prevent automatic loading at boot time
• Restrict access to firmware-attributes sysfs paths using appropriate file permissions
• Temporarily disable fwupd service until the kernel is updated

# Configuration example
# Unload the vulnerable module
sudo modprobe -r hp_bioscfg

# Blacklist the module to prevent automatic loading
echo "blacklist hp_bioscfg" | sudo tee /etc/modprobe.d/hp-bioscfg-blacklist.conf

# Verify module is not loaded
lsmod | grep hp_bioscfg

# Optionally stop fwupd service until patched
sudo systemctl stop fwupd.service
sudo systemctl disable fwupd.service