CVE-2025-38587 – A race condition vulnerability in the Linux ker... (How to Fix)

Q: What is the severity of CVE-2025-38587?

CVE-2025-38587 has a CVSS score of 5.5 (MEDIUM). A race condition vulnerability in the Linux kernel's IPv6 routing subsystem could cause an infinite loop in the fib6_info_uses_dev() function when RCU protection is insufficient. This affects Linux systems with IPv6 enabled, potentially leading to denial of service. Kernel-level access is required to trigger this vulnerability.

📋 TL;DR

A race condition vulnerability in the Linux kernel's IPv6 routing subsystem could cause an infinite loop in the fib6_info_uses_dev() function when RCU protection is insufficient. This affects Linux systems with IPv6 enabled, potentially leading to denial of service. Kernel-level access is required to trigger this vulnerability.

💻 Affected Systems

Products:

Linux Kernel

Versions: Specific affected versions not explicitly stated in CVE, but patches exist in stable kernel trees.

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires IPv6 to be enabled and configured. Systems without IPv6 or with IPv6 disabled are not affected.

📦 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

Kernel panic or system freeze requiring hard reboot, causing extended service disruption.

🟠

Likely Case

Local denial of service affecting network connectivity on the affected system.

🟢

If Mitigated

Minimal impact with proper access controls limiting local user privileges.

🌐 Internet-Facing: LOW - Requires local access to trigger, not directly exploitable over network.

🏢 Internal Only: MEDIUM - Malicious local users or compromised accounts could cause denial of service.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and ability to manipulate IPv6 routing tables. Race condition exploitation requires precise timing.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patched in stable kernel versions via commits referenced in CVE

Vendor Advisory: https://git.kernel.org/stable/c/16d21816c0918f8058b5fc14cbe8595d62046e2d

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from distribution vendor. 2. Reboot system to load new kernel. 3. Verify kernel version after reboot.

🔧 Temporary Workarounds

Disable IPv6

all

Completely disable IPv6 networking to eliminate attack surface

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

Restrict local user access and implement least privilege principles
Monitor system logs for kernel panics or unusual network behavior

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with distribution's security advisories. Vulnerable if running unpatched kernel with IPv6 enabled.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version matches patched version from vendor advisory and test IPv6 functionality remains operational.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
High CPU usage in kernel processes
Network connectivity issues in system logs

Network Indicators:

Sudden loss of IPv6 connectivity
Unusual IPv6 routing table changes

SIEM Query:

source="kernel" AND ("panic" OR "oops" OR "BUG") AND process="kernel"

📊 Metadata

CVE ID: CVE-2025-38587

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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