CVE-2026-23158 Overview
A use-after-free vulnerability has been identified in the Linux kernel's gpio-virtuser subsystem within the configfs release path. The flaw occurs when the gpio_virtuser_device_config_group_release() function uses guard(mutex) to protect the device structure, but the device is freed before the guard cleanup runs. This causes mutex_unlock() to operate on freed memory, resulting in a slab use-after-free condition.
The vulnerability exists because the mutex and device structure are destroyed while still inside the guard(mutex) scope. When the function returns, the guard cleanup invokes mutex_unlock(&dev->lock) on already-freed memory, leading to memory corruption.
Critical Impact
Local attackers with access to configfs may be able to trigger a use-after-free condition in the Linux kernel, potentially leading to system instability, denial of service, or privilege escalation.
Affected Products
- Linux kernel with gpio-virtuser configfs support enabled
- Systems using GPIO virtual user interface via configfs
- Kernel versions prior to the security patches referenced in the fix commits
Discovery Timeline
- 2026-02-14 - CVE-2026-23158 published to NVD
- 2026-02-18 - Last updated in NVD database
Technical Details for CVE-2026-23158
Vulnerability Analysis
This use-after-free vulnerability arises from improper mutex lifetime management in the gpio-virtuser configfs release path. The guard(mutex) construct in the Linux kernel provides automatic mutex acquisition and release via cleanup handlers. However, in gpio_virtuser_device_config_group_release(), the device structure containing the mutex is freed while the guard is still active.
The sequence of operations that triggers the vulnerability is as follows: the release function acquires the mutex via guard(mutex), performs an activation check, then calls mutex_destroy() and kfree() on the device structure. When the function scope ends, the guard cleanup handler attempts to call mutex_unlock() on &dev->lock, which now points to freed slab memory.
This type of use-after-free in kernel space can have significant security implications, as it may allow an attacker to manipulate kernel memory structures for privilege escalation or cause system crashes.
Root Cause
The root cause is the improper scoping of the guard(mutex) protection in the configfs release handler. The mutex guard extends beyond the point where the protected resource is destroyed. The fix limits the mutex lifetime by using scoped_guard() only around the activation check, ensuring the lock is released before mutex_destroy() and kfree() are called.
Attack Vector
To exploit this vulnerability, an attacker would need local access to the system with permissions to interact with the gpio-virtuser configfs interface. The attack involves triggering the release path in a manner that allows manipulation of the freed memory between the kfree() call and the subsequent mutex_unlock() operation.
The vulnerability is exploited through the configfs filesystem interface when releasing gpio-virtuser device configurations. An attacker with appropriate privileges could potentially race the memory allocator to reclaim and manipulate the freed slab memory before the guard cleanup executes, potentially corrupting kernel data structures.
Detection Methods for CVE-2026-23158
Indicators of Compromise
- Kernel crash logs indicating use-after-free in gpio-virtuser or configfs subsystems
- KASAN (Kernel Address Sanitizer) reports showing slab-use-after-free on mutex_unlock() calls
- System instability or unexpected kernel panics when interacting with GPIO virtual user configurations
- Memory corruption errors in kernel logs related to the gpio subsystem
Detection Strategies
- Enable KASAN (Kernel Address Sanitizer) in kernel builds to detect use-after-free memory accesses at runtime
- Monitor kernel logs for stack traces involving gpio_virtuser_device_config_group_release() and mutex operations
- Implement ftrace or eBPF tracing on configfs release operations to detect anomalous behavior
- Use kernel debugging tools like SLUB debugging to detect memory corruption patterns
Monitoring Recommendations
- Configure alerting for kernel oops or panic events related to GPIO or configfs subsystems
- Monitor /sys/kernel/debug/ entries for gpio-related memory debugging information if available
- Implement centralized logging for kernel messages with filters for memory corruption warnings
- Consider deploying SentinelOne Singularity for real-time kernel-level threat detection and behavioral monitoring
How to Mitigate CVE-2026-23158
Immediate Actions Required
- Update the Linux kernel to a patched version that includes the fix for this vulnerability
- Review and restrict access to configfs interfaces, particularly for gpio-virtuser configurations
- Audit systems for unauthorized local users who may have access to trigger the vulnerable code path
- Consider temporarily disabling the gpio-virtuser module if not required for production operations
Patch Information
The Linux kernel development team has released patches to address this vulnerability. The fix modifies the mutex lifetime management by using scoped_guard() only around the activation check, ensuring proper sequencing of lock release before memory deallocation.
Patches are available through the following kernel commits:
Workarounds
- Restrict access to the /sys/kernel/config/gpio-virtuser/ directory to trusted users only
- Disable the gpio-virtuser kernel module if it is not required: modprobe -r gpio-virtuser
- Implement strict access controls on configfs mount points to limit exposure
- Apply kernel security hardening options such as SMEP/SMAP to make exploitation more difficult
# Disable gpio-virtuser module if not required
modprobe -r gpio-virtuser
# Blacklist the module to prevent automatic loading
echo "blacklist gpio-virtuser" >> /etc/modprobe.d/blacklist-gpio-virtuser.conf
# Restrict configfs permissions (if applicable)
chmod 700 /sys/kernel/config/gpio-virtuser/
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
