CVE-2026-64041: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-64041 Overview

CVE-2026-64041 is a buffer overflow vulnerability in the Linux kernel's ALSA System on Chip (ASoC) subsystem, specifically in the fs210x codec driver. The flaw resides in the fs210x_effect_scene_info() function, where strscpy() was invoked using strlen(SRC) + 1 as the size argument instead of sizeof(DST). When the source string length equals or exceeds the destination buffer size, the copy operation writes past the destination boundary, producing a kernel-space buffer overflow [CWE-120].

Critical Impact
A local authenticated user can trigger memory corruption in the kernel, potentially leading to privilege escalation, information disclosure, or denial of service through the ASoC fs210x codec interface.

Affected Products

Linux kernel versions containing the fs210x ASoC codec driver prior to the fix commits
Linux stable branches referenced by commits 0d435a7ebcd4, 1ddf678bb75b, and 6daefdf1cd3c
Distributions shipping the vulnerable ASoC fs210x codec module

Discovery Timeline

2026-07-19 - CVE-2026-64041 published to NVD
2026-07-20 - Last updated in NVD database

Technical Details for CVE-2026-64041

Vulnerability Analysis

The vulnerability exists in the ASoC (ALSA System on Chip) fs210x codec driver, which handles audio effect scene metadata. The function fs210x_effect_scene_info() copies a string into a fixed-size destination buffer using strscpy(DST, SRC, strlen(SRC) + 1). This construction defeats the primary safety property of strscpy(), which is designed to bound the copy to the destination size.

When strlen(SRC) >= sizeof(DST), the third argument exceeds the destination capacity. The routine then writes strlen(SRC) + 1 bytes into a smaller buffer, corrupting adjacent kernel memory. The correct idiom is strscpy(DST, SRC, sizeof(DST)) or the newer two-argument variant that defaults to sizeof(DST).

Root Cause

The root cause is a misuse of the strscpy() API. Developers passed the source length as the bound rather than the destination capacity, negating the truncation guarantee. This pattern is a well-known anti-pattern that reintroduces the exact class of buffer overflow that strscpy() was created to prevent.

Attack Vector

Exploitation requires local access with low privileges on a system loading the fs210x codec driver. An attacker with the ability to invoke the affected ALSA control interface can supply a string longer than the destination buffer. The resulting out-of-bounds write occurs in kernel context and may be leveraged for privilege escalation or to crash the kernel. Because the attack vector is local and the affected code path is reachable through user-controlled audio control operations, the practical impact is confined to systems where the vulnerable codec is present and accessible.

No public proof-of-concept exploit has been published. Technical details are available in the upstream fix commits.

Detection Methods for CVE-2026-64041

Indicators of Compromise

Kernel oops or panic messages referencing fs210x_effect_scene_info or the ASoC subsystem in dmesg
Unexpected process termination or system instability following ALSA control operations on fs210x-based audio devices
KASAN reports indicating out-of-bounds writes originating from the fs210x codec driver

Detection Strategies

Enable CONFIG_KASAN on test kernels to identify out-of-bounds writes triggered by the fs210x code path
Audit loaded kernel modules with lsmod | grep fs210x to determine exposure across the fleet
Compare running kernel versions against the fixed commits 0d435a7ebcd4, 1ddf678bb75b, and 6daefdf1cd3c

Monitoring Recommendations

Ingest kernel logs into a central log platform and alert on ASoC-related crash signatures
Monitor for unexpected loads of the fs210x module on systems that should not use this codec
Track privilege escalation indicators such as unexpected UID transitions following audio subsystem activity

How to Mitigate CVE-2026-64041

Immediate Actions Required

Apply the upstream Linux kernel patches referenced by commits 0d435a7ebcd4e97e47673c1ab6fb27f973a053ec, 1ddf678bb75b6383c775ece61d40956c441d8a26, and 6daefdf1cd3c56483f61970a76c0ad6028e4118f
Rebuild and redeploy kernels from patched stable branches across affected systems
Restrict local access on multi-user systems that expose the fs210x codec

Patch Information

The fix replaces strscpy(DST, SRC, strlen(SRC) + 1) with the correct form strscpy(DST, SRC, sizeof(DST)). Patches are available in the mainline and stable trees at Linux Kernel Commit 0d435a7e, Linux Kernel Commit 1ddf678b, and Linux Kernel Commit 6daefdf1.

Workarounds

Blacklist the fs210x kernel module on systems that do not require this codec by adding blacklist snd_soc_fs210x to /etc/modprobe.d/
Restrict access to ALSA control devices under /dev/snd/ to trusted users through group permissions
Enforce least-privilege policies limiting which users can interact with the audio subsystem

bash

# Configuration example: blacklist the vulnerable codec module
echo "blacklist snd_soc_fs210x" | sudo tee /etc/modprobe.d/cve-2026-64041.conf
sudo depmod -a
sudo update-initramfs -u