CVE-2024-40994 – This CVE describes an integer overflow vulnerab... (How to Fix)

Q: What is the severity of CVE-2024-40994?

CVE-2024-40994 has a CVSS score of 7.8 (HIGH). This CVE describes an integer overflow vulnerability in the Linux kernel's Precision Time Protocol (PTP) subsystem. When setting the maximum number of virtual clocks via the max_vclocks_store function, a multiplication operation can overflow on 32-bit systems, potentially leading to memory corruption. This affects Linux systems with PTP functionality enabled, particularly 32-bit architectures.

📋 TL;DR

This CVE describes an integer overflow vulnerability in the Linux kernel's Precision Time Protocol (PTP) subsystem. When setting the maximum number of virtual clocks via the max_vclocks_store function, a multiplication operation can overflow on 32-bit systems, potentially leading to memory corruption. This affects Linux systems with PTP functionality enabled, particularly 32-bit architectures.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected versions not explicitly stated in CVE description; typically affects kernel versions before the fix commits listed in references

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ✅ No

Notes: Requires PTP subsystem to be enabled and accessible via sysfs. 32-bit systems are primarily affected due to integer overflow in 4 * max calculation.

📦 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

Successful exploitation could lead to kernel memory corruption, resulting in system crashes (denial of service), privilege escalation, or arbitrary code execution in kernel context.

🟠

Likely Case

Most probable impact is kernel panic or system crash leading to denial of service, requiring system reboot to recover.

🟢

If Mitigated

With proper access controls limiting write access to the vulnerable sysfs interface, impact is reduced to denial of service for privileged users only.

🌐 Internet-Facing: LOW - This requires local access to the system's sysfs interface, not directly exploitable over network.

🏢 Internal Only: MEDIUM - Requires local access but could be exploited by malicious users or compromised applications with appropriate permissions.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires write access to /sys/class/ptp/ptpX/max_vclocks interface. No public exploit code identified at this time.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 4b03da87d0b7074c93d9662c6e1a8939f9b8b86e, 666e934d749e50a37f3796caaf843a605f115b6f, 81d23d2a24012e448f651e007fac2cfd20a45ce0, d50d62d5e6ee6aa03c00bddb91745d0b632d3b0f, e1fccfb4638ee6188377867f6015d0ce35764a8e

Vendor Advisory: https://git.kernel.org/stable/c/4b03da87d0b7074c93d9662c6e1a8939f9b8b86e

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Check with your distribution vendor for specific patched kernel packages. 3. Reboot system after kernel update.

🔧 Temporary Workarounds

Restrict sysfs access

linux

Limit write access to the vulnerable sysfs interface to prevent unauthorized users from triggering the vulnerability

chmod 644 /sys/class/ptp/ptp*/max_vclocks
chown root:root /sys/class/ptp/ptp*/max_vclocks

Disable PTP subsystem

linux

Remove or disable PTP functionality if not required

modprobe -r ptp
echo 'blacklist ptp' >> /etc/modprobe.d/blacklist.conf

🧯 If You Can't Patch

Implement strict access controls on /sys/class/ptp/ptp*/max_vclocks to prevent unauthorized writes
Monitor system logs for access attempts to PTP sysfs interfaces and implement alerting

🔍 How to Verify

Check if Vulnerable:

Check if /sys/class/ptp/ptp*/max_vclocks exists and kernel version is before the fix commits

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes the fix commits: grep -q '4b03da87d0b7074c93d9662c6e1a8939f9b8b86e\|666e934d749e50a37f3796caaf843a605f115b6f\|81d23d2a24012e448f651e007fac2cfd20a45ce0\|d50d62d5e6ee6aa03c00bddb91745d0b632d3b0f\|e1fccfb4638ee6188377867f6015d0ce35764a8e' /proc/version

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
OOM killer activity related to PTP
Access denials to /sys/class/ptp/ptp*/max_vclocks

Network Indicators:

None - this is a local vulnerability

SIEM Query:

source="kernel" AND ("ptp" OR "max_vclocks" OR "kernel panic")

📊 Metadata

CVE ID: CVE-2024-40994

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-190

Published: July 12, 2024

Last Updated: November 3, 2025

🔗 References

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🔗 Related Vulnerabilities

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