CVE-2026-98055: Linux Kernel Privilege Escalation Vulnerability

CVE-2026-98055 Overview

CVE-2026-98055 is a Linux kernel vulnerability in the ASoC Intel avs driver. The flaw affects the PCI probe path, specifically avs_pci_probe(), which fails to check the return code of snd_hdac_ext_bus_get_ml_capabilities(). The driver also neglects to clean up the hlink list when subsequent initialization steps fail. The fix updates the error path to verify the capability-fetch result and to release bus resources before returning on failure.

Critical Impact
Improper error handling during HD-Audio multi-link capability fetch can leave kernel resources in an inconsistent state, leading to resource leaks or instability on Intel audio hardware initialization failures.

Affected Products

Linux kernel ASoC Intel avs driver
Systems using Intel HD-Audio with multi-link (ML) extensions
Distributions shipping affected mainline kernel versions prior to the referenced stable commits

Discovery Timeline

2026-09-25 - CVE-2026-98055 published to NVD
2026-09-30 - Last updated in NVD database

Technical Details for CVE-2026-98055

Vulnerability Analysis

The vulnerability resides in avs_pci_probe() within the Intel Audio-DSP (avs) ASoC driver. During probe, the driver calls snd_hdac_ext_bus_get_ml_capabilities() to enumerate HD-Audio multi-link capabilities. The original code did not inspect the return value of this call. A failure in capability retrieval could allow probe to continue with partially initialized bus state.

A second defect in the same function compounds the issue. When snd_hdac_ext_bus_get_ml_capabilities() succeeds but a later step in avs_pci_probe() fails, the hlink list previously allocated by the HD-Audio extended bus is not released before the error path returns. This leaves linked-list entries dangling in kernel memory.

The net effect is a kernel resource management defect on the device initialization path. Repeated probe failures or driver reload cycles can accumulate leaked objects and leave the HD-Audio bus state inconsistent.

Root Cause

The root cause is missing error checking combined with incomplete cleanup. The driver treats snd_hdac_ext_bus_get_ml_capabilities() as infallible and omits an unwind step for the hlink list when later probe stages fail. This is a classic error-handling omission in a device-probe sequence.

Attack Vector

The defect is reached through the normal PCI probe flow for Intel audio controllers. Triggering the error paths requires conditions in which the HD-Audio extended bus capability query fails or a subsequent probe step fails. Exploitation requires local access to a system with the affected hardware and driver loaded. The vulnerability is a reliability and resource-management issue rather than a confirmed remote attack vector.

The fix is distributed across four stable-tree commits referenced below. See the upstream patches for the exact code changes applied to avs_pci_probe().

Detection Methods for CVE-2026-98055

Indicators of Compromise

Kernel log entries from the avs driver indicating probe failure or HD-Audio multi-link capability errors.
dmesg warnings referencing snd_hdac_ext_bus_get_ml_capabilities returning non-zero status.
Increasing kernel slab usage associated with HD-Audio extended-link objects after repeated module load or device rebind cycles.

Detection Strategies

Inventory running kernel versions against the fixed stable-tree commits listed in the upstream references.
Monitor system logs for repeated avs driver probe failures on Intel audio-equipped endpoints.
Use kernel memory diagnostics such as kmemleak on test systems that exhibit audio initialization errors.

Monitoring Recommendations

Centralize kernel logs from Linux endpoints and alert on avs or snd_hdac_ext error patterns.
Track kernel version drift across the fleet to confirm patch adoption.
Correlate driver probe failures with hardware events to isolate affected systems.

How to Mitigate CVE-2026-98055

Immediate Actions Required

Identify Linux hosts running kernels that predate the fix referenced in the upstream stable commits.
Schedule kernel updates to a version containing the patched avs_pci_probe() error path.
Prioritize systems with Intel HD-Audio hardware where the avs driver is loaded.

Patch Information

The fix is applied through the following upstream commits in the Linux stable tree:

Apply the kernel update supplied by your Linux distribution that incorporates these commits.

Workarounds

If a patched kernel is not immediately available, unload the snd_soc_avs module on systems where Intel audio functionality is not required.
Blacklist the avs driver via /etc/modprobe.d/ on affected non-audio workloads to prevent probe execution.
Avoid repeated driver rebind operations on systems exhibiting HD-Audio capability-fetch failures until patched.

bash

# Verify kernel version and check if avs module is loaded
uname -r
lsmod | grep snd_soc_avs

# Temporarily unload the driver if audio is not required
sudo modprobe -r snd_soc_avs

# Persistently blacklist the module until the kernel is patched
echo "blacklist snd_soc_avs" | sudo tee /etc/modprobe.d/blacklist-avs.conf