CVE-2025-38552 – This CVE addresses a race condition vulnerabili... (How to Fix)

Q: What is the severity of CVE-2025-38552?

CVE-2025-38552 has a CVSS score of 7.8 (HIGH). This CVE addresses a race condition vulnerability in the Linux kernel's MPTCP (Multipath TCP) implementation where subflow failures and subflow creation operations can occur simultaneously without proper synchronization. This could allow attackers to cause denial of service or potentially execute arbitrary code with kernel privileges. All Linux systems using MPTCP functionality are affected.

📋 TL;DR

This CVE addresses a race condition vulnerability in the Linux kernel's MPTCP (Multipath TCP) implementation where subflow failures and subflow creation operations can occur simultaneously without proper synchronization. This could allow attackers to cause denial of service or potentially execute arbitrary code with kernel privileges. All Linux systems using MPTCP functionality are affected.

💻 Affected Systems

Products:

Linux Kernel

Versions: Linux kernel versions with MPTCP support before the fix commits (specific versions depend on distribution backports)

Operating Systems: Linux distributions with MPTCP enabled

Default Config Vulnerable: ✅ No

Notes: Only vulnerable if MPTCP is enabled and in use. Many distributions don't enable MPTCP by default.

📦 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...

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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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel memory corruption leading to arbitrary code execution with kernel privileges, potentially resulting in full system compromise.

🟠

Likely Case

Denial of service through kernel panic or system crash, disrupting network connectivity and system availability.

🟢

If Mitigated

Limited impact if MPTCP is disabled or systems are not using multipath TCP connections.

🌐 Internet-Facing: MEDIUM - Requires network access and MPTCP usage, but could be triggered remotely via crafted network packets.

🏢 Internal Only: MEDIUM - Internal attackers could exploit if they have network access to vulnerable systems.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: HIGH

Exploitation requires precise timing to trigger the race condition and knowledge of MPTCP implementation details.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Linux kernel with commits 659da22dee5ff316ba63bdaeeac7b58b5442f6c2, 7c96d519ee15a130842a6513530b4d20acd2bfcd, c476d627584b7589a134a8b48dd5c6639e4401c5, def5b7b2643ebba696fc60ddf675dca13f073486, f81b6fbe13c7fc413b5158cdffc6a59391a2a8db

Vendor Advisory: https://git.kernel.org/stable/c/659da22dee5ff316ba63bdaeeac7b58b5442f6c2

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Check your distribution's security advisories for backported patches. 3. Reboot system after kernel update.

🔧 Temporary Workarounds

Disable MPTCP

linux

Disable MPTCP functionality if not required

sysctl -w net.mptcp.enabled=0
echo 'net.mptcp.enabled = 0' >> /etc/sysctl.conf
sysctl -p

🧯 If You Can't Patch

Disable MPTCP using sysctl commands
Implement network segmentation to limit access to systems using MPTCP

🔍 How to Verify

Check if Vulnerable:

Check if MPTCP is enabled: sysctl net.mptcp.enabled. Check kernel version against distribution security advisories.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes the fix commits. Check with: uname -r and compare with patched versions from your distribution.

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs
MPTCP-related error messages in dmesg
System crash/reboot events

Network Indicators:

Unusual MPTCP connection patterns
MP_FAIL option manipulation attempts

SIEM Query:

Search for kernel panic events or MPTCP-related errors in system logs

📊 Metadata

CVE ID: CVE-2025-38552

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

EPSS Score: 0.02% exploit probability (2.6th percentile)

Published: August 16, 2025

Last Updated: January 7, 2026

🔗 References

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