CVE-2025-39757 – A Linux kernel vulnerability in the ALSA USB au... (How to Fix)

Q: What is the severity of CVE-2025-39757?

CVE-2025-39757 has a CVSS score of 7.1 (HIGH). A Linux kernel vulnerability in the ALSA USB audio subsystem allows out-of-bounds memory access when processing malicious UAC3 audio device descriptors. This affects systems using USB audio devices with Linux kernels containing the vulnerable code. Attackers could potentially crash the system or execute arbitrary code.

📋 TL;DR

A Linux kernel vulnerability in the ALSA USB audio subsystem allows out-of-bounds memory access when processing malicious UAC3 audio device descriptors. This affects systems using USB audio devices with Linux kernels containing the vulnerable code. Attackers could potentially crash the system or execute arbitrary code.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific kernel versions containing the vulnerable ALSA USB audio code (exact versions would need to be determined from git commits)

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems with USB audio support enabled in kernel (common in desktop/laptop systems). Servers without USB audio may not be vulnerable.

📦 What is this software?

Debian Linux by Debian

View all CVEs affecting Debian Linux →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

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Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic, system crash, or potential arbitrary code execution with kernel privileges leading to complete system compromise.

🟠

Likely Case

System instability, kernel panic, or denial of service through crashes when connecting malicious USB audio devices.

🟢

If Mitigated

No impact if patched or if malicious USB devices are prevented from connecting to the system.

🌐 Internet-Facing: LOW - Requires physical or local USB device access, not directly exploitable over network.

🏢 Internal Only: MEDIUM - Malicious USB devices could be plugged into vulnerable systems by insiders or through physical access.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires physical access to connect malicious USB audio device or ability to modify USB device descriptors. No known public exploits as of analysis.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 1034719fdefd26caeec0a44a868bb5a412c2c1a5, 275e37532e8ebe25e8a4069b2d9f955bfd202a46, 47ab3d820cb0a502bd0074f83bb3cf7ab5d79902, 786571b10b1ae6d90e1242848ce78ee7e1d493c4, 799c06ad4c9c790c265e8b6b94947213f1fb389c

Vendor Advisory: https://git.kernel.org/stable/c/1034719fdefd26caeec0a44a868bb5a412c2c1a5

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Reboot system to load new kernel. 3. Check with distribution vendor for specific patched kernel versions.

🔧 Temporary Workarounds

Disable USB audio support

linux

Remove or blacklist USB audio kernel modules to prevent USB audio device usage

echo 'blacklist snd-usb-audio' >> /etc/modprobe.d/blacklist-usb-audio.conf
rmmod snd-usb-audio

Restrict USB device access

linux

Use USBGuard or similar tools to restrict which USB devices can connect

apt-get install usbguard
usbguard generate-policy > /etc/usbguard/rules.conf

🧯 If You Can't Patch

Implement strict physical security controls to prevent unauthorized USB device connections
Use USB port blockers or disable USB ports on critical systems

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with patched versions from distribution vendor. Check if snd-usb-audio module is loaded: lsmod | grep snd-usb-audio

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is updated to patched version. Check that USB audio devices still function properly after patch.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages in /var/log/kern.log or dmesg
ALSA subsystem errors related to USB audio

Network Indicators:

No network indicators - this is a local USB-based vulnerability

SIEM Query:

source="kern.log" AND "kernel panic" OR "ALSA" AND "USB" AND "error"

📊 Metadata

CVE ID: CVE-2025-39757

CVSS v3 Score: 7.1 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CWE: CWE-125

EPSS Score: 0.01% exploit probability (1th percentile)

Published: September 11, 2025

Last Updated: January 9, 2026

🔗 References

https://git.kernel.org/stable/c/1034719fdefd26caeec0a44a868bb5a412c2c1a5 Patch
https://git.kernel.org/stable/c/275e37532e8ebe25e8a4069b2d9f955bfd202a46 Patch
https://git.kernel.org/stable/c/47ab3d820cb0a502bd0074f83bb3cf7ab5d79902 Patch
https://git.kernel.org/stable/c/786571b10b1ae6d90e1242848ce78ee7e1d493c4 Patch
https://git.kernel.org/stable/c/799c06ad4c9c790c265e8b6b94947213f1fb389c Patch
https://git.kernel.org/stable/c/7ef3fd250f84494fb2f7871f357808edaa1fc6ce Patch
https://git.kernel.org/stable/c/ae17b3b5e753efc239421d186cd1ff06e5ac296e Patch
https://git.kernel.org/stable/c/dfdcbcde5c20df878178245d4449feada7d5b201 Patch
https://git.kernel.org/stable/c/ecfd41166b72b67d3bdeb88d224ff445f6163869 Patch
https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html Third Party Advisory,Mailing List
https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html Third Party Advisory,Mailing List

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