CVE-2024-40931 – This CVE addresses an uninitialized variable vu... (How to Fix)

📋 TL;DR

This CVE addresses an uninitialized variable vulnerability in the Linux kernel's MPTCP (Multipath TCP) implementation. Attackers could potentially trigger retransmission issues leading to denial of service or other undefined behavior. Systems running vulnerable Linux kernel versions with MPTCP enabled are affected.

💻 Affected Systems

Products:

Linux Kernel

Versions: Specific kernel versions containing the vulnerable MPTCP commit before the fix

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ✅ No

Notes: Only affects systems with MPTCP enabled and configured. MPTCP is not enabled by default in most Linux distributions.

📦 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 →

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 or system crash leading to complete denial of service, potentially allowing further exploitation through memory corruption.

🟠

Likely Case

MPTCP connection instability, retransmission issues, or denial of service for affected network connections.

🟢

If Mitigated

Minor performance impact or connection establishment failures when MPTCP is used.

🌐 Internet-Facing: MEDIUM - Requires MPTCP to be enabled and accessible, which is not default in most configurations.

🏢 Internal Only: LOW - Requires specific MPTCP usage and network conditions to trigger.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Discovered by syzkaller fuzzer. Exploitation requires specific network conditions and MPTCP usage patterns.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commit 208cd22ef5e57f82d38ec11c1a1703f9401d6dde or later

Vendor Advisory: https://git.kernel.org/stable/c/208cd22ef5e57f82d38ec11c1a1703f9401d6dde

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commit
2. Reboot system to load new kernel
3. Verify MPTCP functionality if used

🔧 Temporary Workarounds

Disable MPTCP

linux

Disable MPTCP functionality if not required

sysctl -w net.mptcp.enabled=0
echo 0 > /proc/sys/net/mptcp/enabled

🧯 If You Can't Patch

Disable MPTCP functionality using sysctl or kernel boot parameters
Implement network segmentation to isolate systems using MPTCP

🔍 How to Verify

Check if Vulnerable:

Check kernel version and verify if MPTCP is enabled: cat /proc/sys/net/mptcp/enabled

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes fix commit and test MPTCP connectivity

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs
MPTCP connection failures in system logs
Network retransmission anomalies

Network Indicators:

Abnormal MPTCP retransmission patterns
MPTCP connection timeouts

SIEM Query:

source="kernel" AND ("MPTCP" OR "retransmit") AND ("panic" OR "error" OR "failure")

📊 Metadata

CVE ID: CVE-2024-40931

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-908

Published: July 12, 2024

Last Updated: November 3, 2025

🔗 References

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🔗 Related Vulnerabilities

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