CVE-2025-37817 – This CVE describes a double-free vulnerability ... (How to Fix)

Q: What is the severity of CVE-2025-37817?

CVE-2025-37817 has a CVSS score of 7.8 (HIGH). This CVE describes a double-free vulnerability in the Linux kernel's MCB (Memory Controller Bridge) subsystem. When mcb_device_register() fails in chameleon_parse_gdd(), the code incorrectly frees the 'mdev' structure twice, potentially leading to memory corruption. This affects systems using the MCB subsystem, typically those with specialized hardware like FPGA-based devices.

📋 TL;DR

This CVE describes a double-free vulnerability in the Linux kernel's MCB (Memory Controller Bridge) subsystem. When mcb_device_register() fails in chameleon_parse_gdd(), the code incorrectly frees the 'mdev' structure twice, potentially leading to memory corruption. This affects systems using the MCB subsystem, typically those with specialized hardware like FPGA-based devices.

💻 Affected Systems

Products:

Linux kernel

Versions: Kernel versions containing the vulnerable chameleon_parse_gdd() function before the fix commits

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable if the MCB subsystem is enabled and used (CONFIG_MCB). This is typically for specialized hardware like FPGA devices, not standard server/workstation configurations.

📦 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 →

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 privilege escalation leading to full system compromise if an attacker can trigger the double-free and control subsequent memory allocations.

🟠

Likely Case

System instability, kernel crashes, or denial of service affecting devices using the MCB subsystem.

🟢

If Mitigated

Limited impact with proper kernel hardening and memory protection mechanisms in place.

🌐 Internet-Facing: LOW - This vulnerability requires local access or specialized hardware interaction.

🏢 Internal Only: MEDIUM - Systems with MCB hardware could be vulnerable to local attackers or malicious processes.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires triggering the specific failure condition in mcb_device_register() and controlling memory allocations. Likely requires local access or specialized hardware interaction.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 4ffe8c9fb561e4427dd1a3056cd5b3685b74f78d, 59f993cd36b6e28a394ba3d977e8ffe5c9884e3b, 7c7f1bfdb2249f854a736d9b79778c7e5a29a150, 96838eb1836fd372e42be5db84f0b333b65146a6, bcc7d58ee5173e34306026bd01e1fbf75e169d37

Vendor Advisory: https://git.kernel.org/stable/c/4ffe8c9fb561e4427dd1a3056cd5b3685b74f78d

Restart Required: Yes

Instructions:

1. Update to a patched kernel version from your distribution vendor. 2. Rebuild kernel if using custom kernel. 3. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable MCB subsystem

linux

If MCB hardware is not needed, disable the subsystem to remove attack surface

echo "blacklist mcb" > /etc/modprobe.d/disable-mcb.conf
rmmod mcb

🧯 If You Can't Patch

Disable MCB subsystem if not required for system functionality
Implement strict access controls to prevent unauthorized users from accessing MCB devices

🔍 How to Verify

Check if Vulnerable:

Check if MCB module is loaded: lsmod | grep mcb. Check kernel version: uname -r and compare with patched versions.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is updated to patched version and MCB module functions correctly if needed.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
MCB subsystem error messages in dmesg
System crash logs

Network Indicators:

None - this is a local vulnerability

SIEM Query:

source="kernel" AND ("panic" OR "double free" OR "mcb" OR "chameleon_parse_gdd")

📊 Metadata

CVE ID: CVE-2025-37817

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-415

EPSS Score: 0.03% exploit probability (6.4th percentile)

Published: May 8, 2025

Last Updated: November 12, 2025

🔗 References

https://git.kernel.org/stable/c/4ffe8c9fb561e4427dd1a3056cd5b3685b74f78d Patch
https://git.kernel.org/stable/c/59f993cd36b6e28a394ba3d977e8ffe5c9884e3b Patch
https://git.kernel.org/stable/c/7c7f1bfdb2249f854a736d9b79778c7e5a29a150 Patch
https://git.kernel.org/stable/c/96838eb1836fd372e42be5db84f0b333b65146a6 Patch
https://git.kernel.org/stable/c/bcc7d58ee5173e34306026bd01e1fbf75e169d37 Patch
https://git.kernel.org/stable/c/c5b8a549ef1fcc6066b037a3962c79d60465ba0b Patch
https://git.kernel.org/stable/c/d70184958b0ea8c0fd52e2b456654b503e769fc8 Patch
https://git.kernel.org/stable/c/df1a5d5c6134224f9298e5189230f9d29ae50cac Patch
https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html Mailing List,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html Mailing List,Third Party Advisory

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