CVE-2026-64023: Linux Kernel Use-After-Free Vulnerability

CVE-2026-64023 Overview

CVE-2026-64023 is a use-after-free vulnerability in the Linux kernel's GPIO aggregator driver (gpio-aggregator). The flaw resides in the cleanup path where aggr->lookups->dev_id is freed before the corresponding entry is removed from the GPIO lookup table. A concurrent thread calling gpiod_find() can iterate the list and invoke gpiod_match_lookup_table(), which unconditionally dereferences dev_id via strcmp(). The upstream fix reverses the order of cleanup operations to eliminate the race.

Critical Impact
Local attackers with the ability to trigger the error path in the GPIO aggregator can achieve memory corruption, potentially leading to privilege escalation or kernel denial of service.

Affected Products

Linux kernel versions containing the gpio-aggregator driver prior to the fixing commits
Distributions shipping vulnerable stable kernel branches
Embedded and IoT systems using GPIO aggregator functionality

Discovery Timeline

2026-07-19 - CVE-2026-64023 published to NVD
2026-07-20 - Last updated in NVD database

Technical Details for CVE-2026-64023

Vulnerability Analysis

The vulnerability is a use-after-free [CWE-416] in the Linux kernel GPIO aggregator subsystem. The GPIO aggregator allows multiple GPIO lines from different controllers to be grouped into a single virtual device. When aggregator construction fails, the error handling path frees the dev_id string belonging to aggr->lookups before removing the lookup entry from the global lookup table list.

Because the lookup table is accessible to other kernel threads, a race window exists between the free of dev_id and the removal of the list entry. During that window, another thread traversing the list through gpiod_find() reaches gpiod_match_lookup_table(), which calls strcmp() on the freed dev_id pointer. This dereference of freed memory can corrupt kernel state or leak sensitive kernel data.

Root Cause

The root cause is incorrect ordering of cleanup operations under concurrent access. The freed object remains reachable from a shared lookup table because unlinking happens after deallocation. The fix reverses the sequence so the entry is removed from the lookup table first, then dev_id is freed, ensuring no concurrent lookup can observe a dangling pointer.

Attack Vector

Exploitation requires local access with the ability to interact with the GPIO aggregator driver, typically via sysfs configuration interfaces such as /sys/bus/platform/drivers/gpio-aggregator/. An attacker triggers the error path during aggregator creation while a second thread performs GPIO lookups. Successful exploitation requires winning a narrow race condition, but the resulting freed-object dereference in kernel context can be leveraged for privilege escalation or system compromise.

No public proof-of-concept is available for this issue. Refer to the upstream kernel commits 30c073cab97a, 7ac4183a41ba, and ea28b286649b for the technical fix details.

Detection Methods for CVE-2026-64023

Indicators of Compromise

Unexpected kernel oops or panic messages referencing gpiod_match_lookup_table or gpiod_find in dmesg and /var/log/kern.log
KASAN (Kernel Address Sanitizer) reports flagging use-after-free in the GPIO aggregator code path
Unusual process activity writing to /sys/bus/platform/drivers/gpio-aggregator/new_device from non-administrative contexts

Detection Strategies

Enable CONFIG_KASAN on test and staging kernels to surface use-after-free conditions during QA
Audit kernel logs for repeated failures in aggregator device creation, which may indicate probing attempts
Compare running kernel version and build against distribution advisories referencing the GPIO aggregator fix commits

Monitoring Recommendations

Monitor writes to GPIO aggregator sysfs interfaces and correlate with the invoking user and process
Alert on kernel crashes or WARN_ON events referencing gpiolib symbols
Track privilege boundary crossings on systems where the GPIO aggregator is loaded but not required for production workloads

How to Mitigate CVE-2026-64023

Immediate Actions Required

Apply vendor-supplied kernel updates that include the three upstream commits fixing the cleanup ordering in gpio-aggregator
Restrict access to GPIO aggregator sysfs interfaces to root and trusted administrative accounts only
Unload or blacklist the gpio-aggregator module on systems that do not require it

Patch Information

The fix reverses the order of cleanup so that the lookup table entry is unlinked before dev_id is freed. The relevant upstream commits are 30c073cab97a, 7ac4183a41ba, and ea28b286649b. Rebuild and deploy kernels containing these commits, or install stable kernel updates from your Linux distribution.

Workarounds

Blacklist the gpio-aggregator module via /etc/modprobe.d/ on hosts that do not need GPIO aggregation
Tighten filesystem permissions on /sys/bus/platform/drivers/gpio-aggregator/ to prevent unprivileged access
Apply mandatory access controls (SELinux, AppArmor) to confine processes capable of interacting with GPIO sysfs entries

bash

# Blacklist the gpio-aggregator module until a patched kernel is deployed
echo "blacklist gpio-aggregator" | sudo tee /etc/modprobe.d/blacklist-gpio-aggregator.conf
sudo update-initramfs -u
sudo modprobe -r gpio-aggregator 2>/dev/null || true