CVE-2025-39706 – A use-after-free vulnerability in the Linux ker... (How to Fix)

Q: What is the severity of CVE-2025-39706?

CVE-2025-39706 has a CVSS score of 5.5 (MEDIUM). A use-after-free vulnerability in the Linux kernel's AMD KFD driver occurs when debugfs entries are destroyed before work queues, causing a kernel NULL pointer dereference. This affects Linux systems with AMD GPU hardware using the KFD driver. The vulnerability can lead to kernel hangs or crashes.

📋 TL;DR

A use-after-free vulnerability in the Linux kernel's AMD KFD driver occurs when debugfs entries are destroyed before work queues, causing a kernel NULL pointer dereference. This affects Linux systems with AMD GPU hardware using the KFD driver. The vulnerability can lead to kernel hangs or crashes.

💻 Affected Systems

Products:

Linux kernel with AMD KFD driver

Versions: Specific kernel versions with the vulnerable commit; check stable kernel trees for exact ranges.

Operating Systems: Linux distributions with affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems with AMD GPU hardware using the KFD driver. Debugfs must be enabled (typically default).

📦 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...

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 leading to system crash and denial of service, requiring physical or remote reboot.

🟠

Likely Case

System instability or hang when specific debugfs operations are performed on AMD GPU systems.

🟢

If Mitigated

Minimal impact if debugfs is disabled or systems don't use AMD GPU hardware with KFD driver.

🌐 Internet-Facing: LOW - Requires local access to debugfs interface, not typically exposed externally.

🏢 Internal Only: MEDIUM - Local users with access to debugfs could trigger system instability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access to debugfs interface. Triggering requires specific timing conditions during process destruction.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions with commit 0333052d90683d88531558dcfdbf2525cc37c233 or later backports

Vendor Advisory: https://git.kernel.org/stable/c/2e58401a24e7b2d4ec619104e1a76590c1284a4c

Restart Required: No

Instructions:

1. Update Linux kernel to patched version from distribution vendor. 2. For custom kernels, apply commit 0333052d90683d88531558dcfdbf2525cc37c233. 3. Recompile and install kernel.

🔧 Temporary Workarounds

Disable debugfs for KFD

all

Prevent access to vulnerable debugfs interface by disabling or restricting debugfs mount.

mount -o remount,nodebug /sys/kernel/debug
echo 0 > /sys/kernel/debug/kfd/enable

🧯 If You Can't Patch

Restrict debugfs access to privileged users only
Disable AMD KFD driver if not required for system functionality

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if /sys/kernel/debug/kfd exists. Vulnerable if using affected kernel with AMD GPU.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes fix commit: 'uname -r' and check git log for commit 0333052d90683d88531558dcfdbf2525cc37c233.

📡 Detection & Monitoring

Log Indicators:

Kernel NULL pointer dereference messages in dmesg
System hangs or crashes related to kfd_process_destroy_wq

Network Indicators:

None - local vulnerability only

SIEM Query:

Search for 'kernel: BUG: unable to handle kernel NULL pointer dereference' with 'kfd' in system logs.

📊 Metadata

CVE ID: CVE-2025-39706

CVSS v3 Score: 5.5 (MEDIUM)

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

CWE: CWE-476

EPSS Score: 0.02% exploit probability (2.6th percentile)

Published: September 5, 2025

Last Updated: January 8, 2026

🔗 References

📤 Share & Export

📄 Export Markdown 📋 Export JSON

🔗 Related Vulnerabilities

If you're affected by CVE-2025-39706, you might also want to check these: