CVE-2025-38588 – A race condition vulnerability in the Linux ker... (How to Fix)

Q: What is the severity of CVE-2025-38588?

CVE-2025-38588 has a CVSS score of 5.5 (MEDIUM). A race condition vulnerability in the Linux kernel's IPv6 routing subsystem can cause an infinite loop in the rt6_nlmsg_size() function when reading RCU-protected linked lists. This affects all Linux systems with IPv6 enabled, potentially leading to denial of service. The vulnerability requires local access to trigger.

📋 TL;DR

A race condition vulnerability in the Linux kernel's IPv6 routing subsystem can cause an infinite loop in the rt6_nlmsg_size() function when reading RCU-protected linked lists. This affects all Linux systems with IPv6 enabled, potentially leading to denial of service. The vulnerability requires local access to trigger.

💻 Affected Systems

Products:

Linux Kernel

Versions: Specific affected versions not specified in CVE, but patches available for multiple stable branches

Operating Systems: All Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems with IPv6 enabled. Most modern Linux distributions have IPv6 enabled 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...

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

Local attacker triggers infinite loop causing kernel panic and system crash, resulting in complete denial of service.

🟠

Likely Case

Local user or process inadvertently triggers the condition causing system instability or temporary unresponsiveness until reboot.

🟢

If Mitigated

With proper access controls, only authorized users can trigger the condition, limiting impact to specific services.

🌐 Internet-Facing: LOW - Requires local access to trigger, cannot be exploited remotely.

🏢 Internal Only: MEDIUM - Local users or processes could trigger denial of service affecting system availability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and timing conditions to trigger the race condition. No known public exploits.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Multiple stable kernel versions with commits: 3c13db3e47e1, 46aeb66e9e54, 54e6fe9dd3b0, 6d345136c9b8, cd8d8bbd9ced

Vendor Advisory: https://git.kernel.org/stable/c/3c13db3e47e170bab19e574404e7b6be45ea873d

Restart Required: No

Instructions:

1. Update Linux kernel to patched version from your distribution's repositories. 2. For custom kernels, apply the relevant patch from kernel.org. 3. Recompile and install the kernel. 4. Reboot into the new kernel.

🔧 Temporary Workarounds

Disable IPv6

all

Completely disable IPv6 networking to prevent the vulnerable code path from being executed

echo 'net.ipv6.conf.all.disable_ipv6 = 1' >> /etc/sysctl.conf
echo 'net.ipv6.conf.default.disable_ipv6 = 1' >> /etc/sysctl.conf
sysctl -p

🧯 If You Can't Patch

Implement strict access controls to limit local user privileges
Monitor system logs for kernel panics or unusual process behavior

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with patched versions from kernel.org. Vulnerable if running unpatched kernel with IPv6 enabled.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes one of the fix commits: 3c13db3e47e1, 46aeb66e9e54, 54e6fe9dd3b0, 6d345136c9b8, or cd8d8bbd9ced

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
System hangs or unresponsiveness
High CPU usage by kernel processes

Network Indicators:

Sudden loss of IPv6 connectivity
Unusual routing table changes

SIEM Query:

source="kernel" AND ("panic" OR "hung" OR "soft lockup") AND process="rt6_nlmsg_size"

📊 Metadata

CVE ID: CVE-2025-38588

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-835

EPSS Score: 0.01% exploit probability (1.8th percentile)

Published: August 19, 2025

Last Updated: January 7, 2026

🔗 References

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