CVE-2024-40980 – This CVE addresses a kernel locking issue in Li... (How to Fix)

Q: What is the severity of CVE-2024-40980?

CVE-2024-40980 has a CVSS score of 5.5 (MEDIUM). This CVE addresses a kernel locking issue in Linux's drop_monitor subsystem where a spin_lock is used in atomic context, causing potential system instability on RT (Real-Time) kernels. The vulnerability can lead to kernel panics or system crashes when the affected code path is triggered. Systems running Linux kernels with RT patches are primarily affected.

📋 TL;DR

This CVE addresses a kernel locking issue in Linux's drop_monitor subsystem where a spin_lock is used in atomic context, causing potential system instability on RT (Real-Time) kernels. The vulnerability can lead to kernel panics or system crashes when the affected code path is triggered. Systems running Linux kernels with RT patches are primarily affected.

💻 Affected Systems

Products:

Linux Kernel

Versions: Specific affected versions not explicitly stated in CVE, but patches exist for multiple stable branches

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ✅ No

Notes: Only affects systems with RT (Real-Time) kernel patches and when drop monitoring functionality is active. Standard Linux kernels are not affected.

📦 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to system crash and denial of service, potentially disrupting critical services on affected systems.

🟠

Likely Case

System instability or crashes when drop monitoring is active on RT kernels, causing service interruptions.

🟢

If Mitigated

Minimal impact if RT kernels aren't used or drop monitoring is disabled.

🌐 Internet-Facing: LOW - This is a kernel-level issue requiring local access or specific kernel operations to trigger.

🏢 Internal Only: MEDIUM - Internal systems running RT kernels with drop monitoring enabled could experience crashes affecting operations.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires triggering specific kernel code paths in drop_monitor subsystem on RT kernels. This appears to be a stability issue rather than a security vulnerability with traditional exploitation vectors.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Multiple stable kernel versions with commits: 07ea878684dfb78a9d4f564c39d07e855a9e242e, 594e47957f3fe034645e6885393ce96c12286334, 76ce2f9125244e1708d29c1d3f9d1d50b347bda0, 96941f29ebcc1e9cbf570dc903f30374909562f5, b3722fb69468693555f531cddda5c30444726dac

Vendor Advisory: https://git.kernel.org/stable/c/07ea878684dfb78a9d4f564c39d07e855a9e242e

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from your distribution vendor. 2. For custom kernels, apply the commit that replaces spin_lock with raw_spin_lock in drop_monitor subsystem. 3. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable drop monitoring

linux

Disable the drop_monitor subsystem to prevent triggering the vulnerable code path

echo 0 > /sys/kernel/debug/tracing/events/net/net_dev_queue/enable
echo 0 > /sys/kernel/debug/tracing/events/net/net_dev_start_xmit/enable

Avoid RT kernel patches

linux

Use standard kernel instead of RT-patched kernel if real-time features aren't required

🧯 If You Can't Patch

Disable all drop monitoring functionality in kernel
Monitor system logs for kernel panic indicators and have recovery procedures ready

🔍 How to Verify

Check if Vulnerable:

Check if running RT kernel: uname -a | grep -i rt. Check if drop monitoring is enabled: cat /sys/kernel/debug/tracing/events/net/net_dev_queue/enable

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes fix commits or check kernel source for raw_spin_lock in drop_monitor code

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
BUG: sleeping function called from invalid context
RCU stall warnings
System crash/reboot events

Network Indicators:

Sudden loss of network monitoring capabilities if drop monitoring was active

SIEM Query:

source="kernel" AND ("sleeping function called from invalid context" OR "trace_drop_common" OR "BUG:")

📊 Metadata

CVE ID: CVE-2024-40980

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-667

Published: July 12, 2024

Last Updated: November 3, 2025

🔗 References

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🔗 Related Vulnerabilities

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