CVE-2026-64482: Linux Kernel Use-After-Free Vulnerability

CVE-2026-64482 Overview

CVE-2026-64482 is a NULL pointer dereference vulnerability in the Linux kernel's Advanced Linux Sound Architecture (ALSA) subsystem, specifically in the Gravis UltraSound (GUS) driver. The flaw resides in snd_gf1_pcm_volume_control(), which fails to validate the return value of snd_ctl_new1() before dereferencing the returned pointer. When memory allocation fails, snd_ctl_new1() returns NULL, and the subsequent access to kctl->id.index triggers a NULL pointer dereference in kernel space. The upstream fix adds a NULL check and returns -ENOMEM when allocation fails.

Critical Impact
A NULL pointer dereference in kernel context can cause a kernel oops or panic, resulting in a local denial of service on affected Linux systems that load the ALSA GUS driver.

Affected Products

Linux kernel (multiple stable branches, per the referenced stable tree commits)
Systems loading the ALSA snd-gusclassic / GUS driver module
Distributions shipping unpatched Linux kernels with ALSA GUS support enabled

Discovery Timeline

2026-07-25 - CVE-2026-64482 published to NVD
2026-07-25 - Last updated in NVD database

Technical Details for CVE-2026-64482

Vulnerability Analysis

The vulnerability exists in the ALSA GUS driver code path that establishes PCM volume controls. The function snd_gf1_pcm_volume_control() invokes snd_ctl_new1() to allocate a new kernel control structure. Under memory pressure, snd_ctl_new1() can return NULL to indicate allocation failure.

The unpatched code immediately dereferences the returned pointer by accessing kctl->id.index without verifying that the pointer is non-NULL. This dereference occurs in kernel context and triggers a page fault at a low virtual address. The resulting kernel oops terminates the offending task and can destabilize the system depending on lock state at the time of the fault.

The defect is a classic missing-return-value check pattern common in older audio drivers. It falls under the Null Pointer Dereference class of memory safety bugs.

Root Cause

The root cause is missing error handling after a memory allocation function. snd_ctl_new1() documents that NULL is a valid return under low-memory conditions, but the caller in the GUS PCM volume path assumed success. The upstream patch adds an explicit NULL check and propagates -ENOMEM back to the caller so initialization aborts cleanly instead of dereferencing an invalid pointer.

Attack Vector

Triggering the flaw requires the ALSA GUS driver to be loaded and a memory allocation for snd_ctl_new1() to fail during PCM volume control creation. This is a local, low-severity denial-of-service condition rather than a remotely exploitable code execution vector. There is no indication in the reference material that the flaw enables privilege escalation or arbitrary write primitives. The vulnerability is reachable only during driver initialization or reconfiguration on hardware that binds the GUS driver.

No verified exploit code is available. See the referenced Linux kernel commits for the sanitized fix, including commit 465075c6 and commit 97f6bdf5.

Detection Methods for CVE-2026-64482

Indicators of Compromise

Kernel oops or panic messages referencing snd_gf1_pcm_volume_control or snd_ctl_new1 in dmesg or /var/log/kern.log
Repeated crashes or module load failures for snd-gusclassic correlated with low-memory conditions
Unexpected termination of audio-related processes during driver initialization

Detection Strategies

Inventory hosts running Linux kernel versions predating the fixes referenced in the stable tree commits and flag those with ALSA GUS support enabled
Parse kernel crash telemetry for NULL pointer dereference stack traces originating in the ALSA GUS PCM path
Correlate kernel module load events (snd-gusclassic) with subsequent kernel error signatures

Monitoring Recommendations

Forward dmesg and kernel crash dumps to a centralized logging pipeline for pattern matching on ALSA subsystem faults
Track kernel package versions across the fleet and alert on hosts that have not received distribution kernel updates addressing the referenced commits
Monitor system memory pressure metrics alongside audio subsystem stability to identify environments most likely to trigger the allocation-failure path

How to Mitigate CVE-2026-64482

Immediate Actions Required

Apply the vendor kernel update from your Linux distribution that incorporates the upstream fixes referenced in the NVD entry
On systems that do not require Gravis UltraSound hardware support, blacklist the snd-gusclassic module to eliminate exposure
Reboot after kernel package updates so the patched kernel image is active

Patch Information

The fix has been merged into the Linux stable tree across multiple branches. Refer to the following upstream commits for the sanitized change that adds the missing NULL check and returns -ENOMEM: commit 465075c6, commit 5e74e5e8, commit 97f6bdf5, commit c7fa99d3, commit eccf8e91, and commit fc5d4f27. Consume the fix through your distribution's kernel update channel rather than cherry-picking manually where possible.

Workarounds

Blacklist the ALSA GUS driver on systems without Gravis UltraSound hardware to prevent the vulnerable code path from loading
Restrict physical and local access on systems where the driver must remain loaded, since triggering the fault requires local conditions
Ensure adequate system memory headroom to reduce the likelihood of snd_ctl_new1() allocation failures

bash

# Configuration example: blacklist the ALSA GUS module
echo "blacklist snd_gusclassic" | sudo tee /etc/modprobe.d/blacklist-snd-gus.conf
sudo depmod -a
sudo update-initramfs -u
# Verify the module is not loaded after reboot
lsmod | grep snd_gus