CVE-2025-38108 – A race condition in the Linux kernel's RED (Ran... (How to Fix)

Q: What is the severity of CVE-2025-38108?

CVE-2025-38108 has a CVSS score of 7.0 (HIGH). A race condition in the Linux kernel's RED (Random Early Detection) queue discipline allows an attacker to cause an underflow of a parent queue's packet counter. This can lead to denial of service or potentially other memory corruption issues. Affects Linux systems using RED queuing with SFQ (Stochastic Fairness Queueing) perturb timer.

📋 TL;DR

A race condition in the Linux kernel's RED (Random Early Detection) queue discipline allows an attacker to cause an underflow of a parent queue's packet counter. This can lead to denial of service or potentially other memory corruption issues. Affects Linux systems using RED queuing with SFQ (Stochastic Fairness Queueing) perturb timer.

💻 Affected Systems

Products:

Linux kernel

Versions: Kernel versions before the fix commits (specific versions vary by distribution)

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable when RED queuing is configured and SFQ perturb timer is active. Not all systems use RED 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...

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 panic or system crash leading to complete denial of service, potentially enabling further exploitation through memory corruption.

🟠

Likely Case

Local denial of service causing network instability or system performance degradation.

🟢

If Mitigated

Minimal impact with proper kernel hardening and network configuration controls.

🌐 Internet-Facing: LOW - Requires local access or ability to manipulate network queuing locally.

🏢 Internal Only: MEDIUM - Could be exploited by malicious local users or through compromised internal accounts.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and ability to manipulate network queuing. Race conditions are timing-dependent and may be difficult to reliably exploit.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 110a47efcf23438ff8d31dbd9c854fae2a48bf98, 2790c4ec481be45a80948d059cd7c9a06bc37493, 2a71924ca4af59ffc00f0444732b6cd54b153d0e, 444ad445df5496a785705019268a8a84b84484bb, 4b755305b2b0618e857fdadb499365b5f2e478d1

Vendor Advisory: https://git.kernel.org/stable/c/110a47efcf23438ff8d31dbd9c854fae2a48bf98

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from your distribution's repositories. 2. Reboot system to load new kernel. 3. Verify kernel version matches patched release.

🔧 Temporary Workarounds

Disable RED queuing

linux

Remove or disable RED queue discipline configuration if not required

tc qdisc del dev <interface> root
Remove RED configuration from network scripts

Disable SFQ perturb timer

linux

Configure SFQ without perturb timer to avoid race condition trigger

tc qdisc add dev <interface> root sfq perturb 0

🧯 If You Can't Patch

Implement strict access controls to prevent unauthorized local users from manipulating network queuing
Monitor system logs for unusual network configuration changes or denial of service symptoms

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if RED queuing is configured: 'uname -r' and 'tc qdisc show'

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is patched and test network stability with RED configuration

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs
Network subsystem errors
Unexpected qdisc changes

Network Indicators:

Sudden network performance degradation
Packet loss anomalies

SIEM Query:

kernel:panic OR kernel:BUG OR network:qdisc_error

📊 Metadata

CVE ID: CVE-2025-38108

CVSS v3 Score: 7.0 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-362

EPSS Score: 0.02% exploit probability (3.6th percentile)

Published: July 3, 2025

Last Updated: December 16, 2025

🔗 References

https://git.kernel.org/stable/c/110a47efcf23438ff8d31dbd9c854fae2a48bf98 Patch
https://git.kernel.org/stable/c/2790c4ec481be45a80948d059cd7c9a06bc37493 Patch
https://git.kernel.org/stable/c/2a71924ca4af59ffc00f0444732b6cd54b153d0e Patch
https://git.kernel.org/stable/c/444ad445df5496a785705019268a8a84b84484bb Patch
https://git.kernel.org/stable/c/4b755305b2b0618e857fdadb499365b5f2e478d1 Patch
https://git.kernel.org/stable/c/85a3e0ede38450ea3053b8c45d28cf55208409b8 Patch
https://git.kernel.org/stable/c/a1bf6a4e9264a685b0e642994031f9c5aad72414 Patch
https://git.kernel.org/stable/c/f569984417a4e12c67366e69bdcb752970de921d Patch
https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html Third Party Advisory,Mailing List
https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html Third Party Advisory,Mailing List

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