CVE-2026-64484: Linux Kernel Use-After-Free Vulnerability

CVE-2026-64484 Overview

CVE-2026-64484 is a NULL pointer dereference vulnerability in the Linux kernel's Advanced Linux Sound Architecture (ALSA) subsystem. The flaw resides in the snd_es1938_mixer() function within the ES1938 sound driver. The function calls snd_ctl_new1() but does not check its return value before dereferencing the returned pointer. Because snd_ctl_new1() can return NULL when memory allocation fails, subsequent pointer access triggers a kernel NULL pointer dereference. The upstream fix adds a NULL check after snd_ctl_new1() and returns -ENOMEM when allocation fails.

Critical Impact
A NULL pointer dereference in the ALSA es1938 driver can crash the kernel, resulting in a local denial of service on affected systems that load the driver.

Affected Products

Linux kernel (mainline) with the ALSA ES1938 driver compiled or loaded
Stable kernel branches referenced by the fixing commits (1949163, 1edd1f0, 41759af, 6c4efeb, 7531a37, 96cad5b, 9e53e99, af01c48)
Distributions redistributing vulnerable kernel versions before applying the ALSA patch

Discovery Timeline

2026-07-25 - CVE-2026-64484 published to NVD
2026-07-25 - Last updated in NVD database

Technical Details for CVE-2026-64484

Vulnerability Analysis

The vulnerability affects the ES1938 (ESS Solo-1) PCI audio driver in the Linux kernel's ALSA subsystem. During mixer initialization, snd_es1938_mixer() invokes snd_ctl_new1() to allocate and initialize a new sound control element. The function returns a pointer to the newly allocated control or NULL if the underlying memory allocation fails.

The pre-patch code path uses the returned pointer directly without validation. When kernel memory pressure or allocator failure causes snd_ctl_new1() to return NULL, the subsequent dereference triggers a kernel oops. The result is a denial of service condition affecting kernel stability.

Root Cause

The root cause is a missing return-value check on snd_ctl_new1() in snd_es1938_mixer(). This is a Null Pointer Dereference class defect [CWE-476]. The fix adds an explicit NULL check immediately after the allocation call and returns -ENOMEM to propagate the failure upward, allowing the caller to abort mixer setup cleanly.

Attack Vector

Exploitation requires the vulnerable snd-es1938 driver to be present and loaded on the target system, which is limited to hardware containing an ESS Solo-1 audio device. Triggering the NULL dereference requires inducing allocation failure during driver mixer initialization. The vector is local and impacts availability. There are no indicators that this issue is exploitable for privilege escalation or code execution.

No public proof-of-concept exploit is available. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog, and the EPSS probability remains low.

See the upstream patch commits, including Kernel Git Commit 1949163 and Kernel Git Commit af01c48, for the exact source change.

Detection Methods for CVE-2026-64484

Indicators of Compromise

Kernel oops or panic entries in dmesg or /var/log/kern.log referencing snd_es1938_mixer or snd_ctl_new1
Unexpected loss of audio functionality followed by driver initialization failures during boot
Repeated -ENOMEM return codes from ALSA control creation on systems using the ES1938 driver

Detection Strategies

Inventory kernel versions across Linux endpoints and compare against the fixing commits referenced in stable branches
Query loaded kernel modules with lsmod | grep snd_es1938 to identify hosts exposing the vulnerable code path
Correlate kernel crash telemetry with ALSA driver initialization events to flag suspected trigger attempts

Monitoring Recommendations

Forward kernel ring buffer output and journalctl -k events to a centralized logging pipeline for retention and analysis
Alert on kernel oops signatures that reference ALSA control functions to detect exploitation attempts or reliability failures
Track package manager events for kernel updates to confirm patch deployment across the fleet

How to Mitigate CVE-2026-64484

Immediate Actions Required

Update the Linux kernel to a version containing the ALSA es1938 return-value check patch supplied by your distribution
On systems that do not require the ESS Solo-1 audio device, blacklist the snd_es1938 module to eliminate exposure
Prioritize patching on multi-user systems where local denial of service directly impacts availability

Patch Information

The fix adds a NULL check after snd_ctl_new1() in snd_es1938_mixer() and returns -ENOMEM on allocation failure. The change has been merged across multiple stable kernel branches. Relevant commits include Kernel Git Commit 1edd1f0, Kernel Git Commit 41759af, Kernel Git Commit 6c4efeb, Kernel Git Commit 7531a37, Kernel Git Commit 96cad5b, and Kernel Git Commit 9e53e99. Apply the vendor-provided kernel package that incorporates these commits.

Workarounds

Blacklist the snd_es1938 module by adding blacklist snd_es1938 to a file under /etc/modprobe.d/ and rebuilding the initramfs
Physically remove or disable the ESS Solo-1 device in BIOS on systems where audio hardware is not required
Restrict local access on affected hosts until the kernel patch is deployed

bash

# Blacklist the vulnerable ALSA driver until the kernel is patched
echo "blacklist snd_es1938" | sudo tee /etc/modprobe.d/blacklist-es1938.conf
sudo update-initramfs -u
sudo reboot