CVE-2025-39989 – This Linux kernel vulnerability (CVE-2025-39989... (How to Fix)

Q: What is the severity of CVE-2025-39989?

CVE-2025-39989 has a CVSS score of 5.5 (MEDIUM). This Linux kernel vulnerability (CVE-2025-39989) causes improper handling of memory errors during copy-from-user operations, leading to kernel panics instead of graceful error recovery. It affects systems running Linux kernel versions 5.17 through the patched version, primarily impacting x86 architectures. The vulnerability can cause system crashes when memory corruption occurs during user-space data copying.

📋 TL;DR

This Linux kernel vulnerability (CVE-2025-39989) causes improper handling of memory errors during copy-from-user operations, leading to kernel panics instead of graceful error recovery. It affects systems running Linux kernel versions 5.17 through the patched version, primarily impacting x86 architectures. The vulnerability can cause system crashes when memory corruption occurs during user-space data copying.

💻 Affected Systems

Products:

Linux kernel

Versions: Linux kernel versions from 5.17 up to the patched version

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Primarily affects x86 architectures; requires memory hardware errors or corruption to trigger

📦 What is this software?

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 leading to system crash and denial of service, potentially causing data loss or service disruption.

🟠

Likely Case

System instability or crashes when memory errors occur during legitimate copy-from-user operations.

🟢

If Mitigated

Graceful error handling with -EFAULT returns to user space when memory errors are detected.

🌐 Internet-Facing: LOW - Requires specific memory corruption conditions and is not directly network-exploitable.

🏢 Internal Only: MEDIUM - Can be triggered by normal system operations when memory hardware errors occur.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires specific memory corruption conditions; not a typical remote code execution vulnerability

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patched in kernel commits referenced in CVE details

Vendor Advisory: https://git.kernel.org/stable/c/0b8388e97ba6a8c033f9a8b5565af41af07f9345

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version 2. Apply specific kernel patches from git.kernel.org 3. Reboot system to load new kernel

🔧 Temporary Workarounds

Disable memory error handling features

linux

Disable MCE (Machine Check Exception) handling features which may reduce system stability monitoring

echo 0 > /sys/devices/system/machinecheck/machinecheck0/check_interval
echo 0 > /sys/devices/system/machinecheck/machinecheck0/check_interval

🧯 If You Can't Patch

Monitor system logs for MCE errors and kernel panics
Implement high-availability configurations to minimize service disruption during crashes

🔍 How to Verify

Check if Vulnerable:

Check kernel version: uname -r and compare against affected versions (5.17+)

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is updated beyond affected range and check for specific patch commits

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
MCE (Machine Check Exception) logs in dmesg
'Hardware Error' messages in system logs

Network Indicators:

None - this is a local kernel vulnerability

SIEM Query:

source="kernel" AND ("panic" OR "MCE" OR "Hardware Error")

📊 Metadata

CVE ID: CVE-2025-39989

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-401

EPSS Score: 0.06% exploit probability (19.4th percentile)

Published: April 18, 2025

Last Updated: November 6, 2025

🔗 References

📤 Share & Export

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🔗 Related Vulnerabilities

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