CVE-2025-21715 – This CVE describes a use-after-free vulnerabili... (How to Fix)

Q: What is the severity of CVE-2025-21715?

CVE-2025-21715 has a CVSS score of 7.8 (HIGH). This CVE describes a use-after-free vulnerability in the Linux kernel's dm9000 network driver. An attacker with local access could potentially exploit this to crash the system or execute arbitrary code with kernel privileges. Systems using the dm9000 network interface driver in affected Linux kernel versions are vulnerable.

📋 TL;DR

This CVE describes a use-after-free vulnerability in the Linux kernel's dm9000 network driver. An attacker with local access could potentially exploit this to crash the system or execute arbitrary code with kernel privileges. Systems using the dm9000 network interface driver in affected Linux kernel versions are vulnerable.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected versions not specified in CVE description, but likely multiple stable kernel versions before the fix commits.

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only vulnerable if dm9000 network driver is loaded and in use. This driver is typically used for Davicom DM9000/DM9010 Ethernet chips.

📦 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...

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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 →

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

Local privilege escalation to kernel-level code execution leading to complete system compromise.

🟠

Likely Case

Kernel panic or system crash causing denial of service.

🟢

If Mitigated

No impact if patched or if dm9000 driver is not loaded.

🌐 Internet-Facing: LOW - This requires local access to exploit.

🏢 Internal Only: MEDIUM - Internal users with local access could potentially exploit this vulnerability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires local access and knowledge of kernel memory layout. Similar to CVE fixed in commit ad297cd2db89.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Linux kernel versions containing fixes from the referenced commits

Vendor Advisory: https://git.kernel.org/stable/c/19e65c45a1507a1a2926649d2db3583ed9d55fd9

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Reboot system to load patched kernel. 3. Verify dm9000 driver is not vulnerable.

🔧 Temporary Workarounds

Disable dm9000 driver

Linux

Prevent loading of vulnerable dm9000 network driver

echo 'blacklist dm9000' > /etc/modprobe.d/blacklist-dm9000.conf
update-initramfs -u
reboot

🧯 If You Can't Patch

Restrict local access to systems using dm9000 driver
Implement strict privilege separation and limit user capabilities

🔍 How to Verify

Check if Vulnerable:

Check if dm9000 driver is loaded: lsmod | grep dm9000. If loaded, check kernel version against patched versions.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is updated and dm9000 driver loads without issues. Check dmesg for any UAF-related errors.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
Use-after-free warnings in dmesg
System crashes during network interface removal

Network Indicators:

Sudden loss of network connectivity on dm9000 interfaces

SIEM Query:

source="kernel" AND ("UAF" OR "use-after-free" OR "dm9000" OR "kernel panic")

📊 Metadata

CVE ID: CVE-2025-21715

CVSS v3 Score: 7.8 (HIGH)

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

CWE: CWE-416

EPSS Score: 0.04% exploit probability (12.3th percentile)

Published: February 27, 2025

Last Updated: November 3, 2025

🔗 References

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