CVE-2025-38063 – A Linux kernel vulnerability in the device mapp... (How to Fix)

Q: What is the severity of CVE-2025-38063?

CVE-2025-38063 has a CVSS score of 5.5 (MEDIUM). A Linux kernel vulnerability in the device mapper (dm) subsystem causes unnecessary I/O throttling for flush operations, potentially degrading system performance. This affects systems using device mapper with specific kernel versions, particularly when XFS filesystem metadata writes are involved. The issue can cause performance degradation but does not allow privilege escalation or data corruption.

📋 TL;DR

A Linux kernel vulnerability in the device mapper (dm) subsystem causes unnecessary I/O throttling for flush operations, potentially degrading system performance. This affects systems using device mapper with specific kernel versions, particularly when XFS filesystem metadata writes are involved. The issue can cause performance degradation but does not allow privilege escalation or data corruption.

💻 Affected Systems

Products:

Linux kernel

Versions: Multiple stable kernel versions including v5.4 and upstream versions before fixes were applied

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires device mapper usage and specific I/O patterns; particularly affects XFS filesystem metadata operations.

📦 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Severe system performance degradation leading to application timeouts, service unavailability, or system hangs during high I/O workloads.

🟠

Likely Case

Reduced I/O performance, increased latency for filesystem operations, and potential slowdown of applications relying on XFS or device mapper.

🟢

If Mitigated

Minimal impact with proper kernel patching; performance returns to normal levels.

🌐 Internet-Facing: LOW - This is a performance issue, not a security vulnerability that allows external exploitation.

🏢 Internal Only: MEDIUM - Can affect system performance and availability for internal services, but doesn't compromise security.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: LOW - The issue occurs naturally during normal system operation with specific I/O patterns.

This is a performance degradation issue, not a traditional security exploit. The 'exploitation' occurs through normal system usage patterns.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Multiple stable kernel commits: 2858cda9a8d95e6deee7e3b0a26adde696a9a4f5, 52aa28f7b1708d76e315d78b5ed397932a1a97c3, 88f7f56d16f568f19e1a695af34a7f4a6ce537a6, 95d08924335f3b6f4ea0b92ebfe4fe0731c502d9, b55a97d1bd4083729a60d19beffe85d4c96680de

Vendor Advisory: https://git.kernel.org/stable/c/2858cda9a8d95e6deee7e3b0a26adde696a9a4f5

Restart Required: Yes

Instructions:

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

🔧 Temporary Workarounds

Disable writeback throttling

linux

Temporarily disable writeback throttling to avoid the performance impact (not recommended for production).

echo 0 > /sys/block/<device>/queue/wbt_lat_usec

Avoid specific I/O patterns

linux

Monitor and avoid workloads that trigger frequent flush operations with device mapper.

🧯 If You Can't Patch

Monitor system performance and I/O latency metrics for degradation
Consider migrating critical workloads to systems with patched kernels

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if device mapper is in use with XFS filesystems experiencing performance issues during flush operations.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes the fix commits and monitor for resolution of I/O throttling issues during flush operations.

📡 Detection & Monitoring

Log Indicators:

Kernel logs showing I/O throttling, increased I/O wait times in system metrics
Performance monitoring alerts for increased I/O latency

SIEM Query:

source="kernel" AND ("throttle" OR "wbt_wait" OR "I/O wait" OR performance_degradation)

📊 Metadata

CVE ID: CVE-2025-38063

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

EPSS Score: 0.02% exploit probability (5th percentile)

Published: June 18, 2025

Last Updated: December 17, 2025

🔗 References

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