CVE-2026-31587: Linux Kernel Use-After-Free Vulnerability

CVE-2026-31587 Overview

CVE-2026-31587 is a use-after-free vulnerability [CWE-416] in the Linux kernel's ASoC (ALSA System on Chip) subsystem, specifically in the Qualcomm q6apm component. The flaw stems from incorrect lifecycle management between the ASoC component and dynamically registered Digital Audio Interfaces (DAIs). Both objects were allocated using device-managed (devm_) APIs, leading to an incorrect free ordering where DAI memory is released while the component still holds references. The issue was detected by KASAN (Kernel Address Sanitizer) during platform-driver remove operations on Qualcomm SoC audio hardware.

Critical Impact
A local low-privileged attacker can trigger a use-after-free condition in the kernel audio subsystem, potentially leading to memory corruption, kernel crash, or local privilege escalation on affected Qualcomm-based Linux systems.

Affected Products

Linux Kernel branches containing the snd_q6apm driver with ASoC topology-based DAI registration
Qualcomm-based platforms using the q6apm audio component (for example, x1e80100 reference platforms)
Distributions shipping vulnerable kernel versions prior to the stable patches listed in the kernel.org commits

Discovery Timeline

2026-04-24 - CVE-2026-31587 published to NVD
2026-04-28 - Last updated in NVD database

Technical Details for CVE-2026-31587

Vulnerability Analysis

The q6apm driver registers DAIs dynamically based on ASoC topology files. Both the component registration and the DAI allocations used device-managed APIs (devm_kmalloc, devm_snd_soc_register_component). Device-managed resources are released in reverse registration order during driver unbind.

Because the component was registered after the DAIs were allocated through snd_soc_register_dai in the topology load path, the DAI memory could be freed before the component teardown completed. When snd_soc_del_component_unlocked later iterated over the component's DAI list, it dereferenced freed memory. The KASAN report captures an 8-byte read at a freed slab address during pdr_notifier_work triggered by a Protocol Domain Restart event.

Root Cause

The root cause is mismatched object lifetimes between a parent (the ASoC component) and its dynamically registered children (DAIs). Allocating both with devm_ APIs caused the resource release framework (devres_release_all) to free the DAI pointers while snd_soc_del_component_unlocked was still walking them, producing a slab-use-after-free condition (CWE-416).

Attack Vector

Exploitation requires local access with low privileges on a system using the affected snd_q6apm driver. A trigger occurs when the audio service domain restarts through the Qualcomm PDR (Protocol Domain Restart) notifier path, invoking apr_remove_device and tearing down the component. An attacker able to influence service restarts, driver unbinding, or repeated topology loads can race the teardown to read or write freed kernel slab memory. The fix moves the component to the unmanaged registration variant so DAI pointers are only freed after the component is fully removed.

No public proof-of-concept is available. See the upstream commits listed under Patch Information for the precise code change.

Detection Methods for CVE-2026-31587

Indicators of Compromise

KASAN slab-use-after-free reports referencing snd_soc_del_component_unlocked in snd_soc_core
Kernel oops or panic traces involving devm_component_release, apr_remove_device, or pdr_notifier_work
Unexpected audio subsystem crashes following audio service restarts on Qualcomm platforms

Detection Strategies

Enable KASAN on test kernels to surface use-after-free conditions in the ASoC q6apm path before deployment
Inventory kernel versions across the fleet and flag hosts running unpatched snd_q6apm builds
Correlate kernel ring buffer (dmesg) entries containing q6apm, apr, or snd_soc_del_component_unlocked across endpoints

Monitoring Recommendations

Forward kernel logs to a centralized SIEM and alert on KASAN reports and unexpected ASoC teardown stacks
Monitor frequency of pdr_notifier_work and apr_remove_device events on Qualcomm endpoints for anomalous patterns
Track driver bind/unbind events for snd_q6apm and parent platform devices such as x1e80100

How to Mitigate CVE-2026-31587

Immediate Actions Required

Apply the upstream stable kernel patches that move q6apm component registration to the unmanaged variant
Restrict local access on affected Qualcomm-based Linux endpoints until patched kernels are deployed
Audit which production systems load the snd_q6apm module and prioritize them for kernel updates

Patch Information

The fix replaces the device-managed component registration in q6apm with the unmanaged snd_soc_register_component API, ensuring the component is torn down before DAI memory is released. The patch has been backported across multiple stable trees. Reference commits:

Workarounds

Unload or blacklist the snd_q6apm module on systems where audio functionality is not required
Limit interactive local access and restrict use of audio APIs to trusted users while patches are pending
Avoid triggering audio service domain restarts on unpatched systems

bash

# Blacklist the vulnerable module until patched kernel is deployed
echo "blacklist snd_q6apm" | sudo tee /etc/modprobe.d/blacklist-q6apm.conf
sudo update-initramfs -u

# Verify running kernel version after update
uname -r

# Confirm the module is not loaded
lsmod | grep snd_q6apm