CVE-2025-38499

5.5 MEDIUM

📋 TL;DR

This Linux kernel vulnerability allows users without proper administrative privileges in the correct user namespace to clone private mount points, potentially exposing hidden filesystems or mount configurations. It affects systems using Linux kernel versions with the flawed clone_private_mnt() function. The issue stems from insufficient CAP_SYS_ADMIN capability checks in specific user namespace contexts.

💻 Affected Systems

Products:

Linux Kernel

Versions: Specific affected versions not explicitly stated in CVE description; likely affects multiple stable kernel versions before the fix commits.

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires user namespace functionality and mount operations; more impactful in containerized environments and systems with multiple user namespaces.

📦 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 →

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

An attacker could bypass mount namespace isolation, access hidden filesystems, escalate privileges, or manipulate mount configurations to compromise system integrity.

🟠

Likely Case

Local users could gain unauthorized access to mount points or filesystems that should be restricted, potentially leading to information disclosure or limited privilege escalation.

🟢

If Mitigated

With proper user namespace configurations and minimal user privileges, the attack surface is significantly reduced, limiting impact to isolated containers or specific user contexts.

🌐 Internet-Facing: LOW - This is a local privilege escalation vulnerability requiring local access to the system.

🏢 Internal Only: MEDIUM - Internal users with shell access could potentially exploit this to bypass mount restrictions within their user namespace.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires understanding of Linux mount namespaces and user namespace capabilities; likely requires local access and some privileges.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 36fecd740de2d542d2091d65d36554ee2bcf9c65, 38628ae06e2a37770cd794802a3f1310cf9846e3, c28f922c9dcee0e4876a2c095939d77fe7e15116, d717325b5ecf2a40daca85c61923e17f32306179, dc6a664089f10eab0fb36b6e4f705022210191d2

Vendor Advisory: https://git.kernel.org/stable/c/36fecd740de2d542d2091d65d36554ee2bcf9c65

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. For distributions: Use package manager (apt/yum/dnf) to update kernel package. 3. Reboot system to load new kernel.

🔧 Temporary Workarounds

Restrict User Namespace Creation

Linux

Limit ability to create user namespaces to reduce attack surface

echo 0 > /proc/sys/user/max_user_namespaces
sysctl -w user.max_user_namespaces=0

Disable Unprivileged User Namespaces

Linux

Prevent non-root users from creating user namespaces

echo 1 > /proc/sys/kernel/unprivileged_userns_clone
sysctl -w kernel.unprivileged_userns_clone=0

🧯 If You Can't Patch

Implement strict user privilege management and limit CAP_SYS_ADMIN capabilities
Use container security profiles (AppArmor/SELinux) to restrict mount operations

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with distribution security advisories; examine if affected kernel commits are present in /proc/version

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version after update; check that fix commits are included in kernel source or distribution changelog

📡 Detection & Monitoring

Log Indicators:

Unusual mount operations in system logs
Failed CAP_SYS_ADMIN capability checks in audit logs
User namespace creation events

Network Indicators:

None - this is a local vulnerability

SIEM Query:

source="kernel" AND ("mount" OR "clone_private_mnt" OR "CAP_SYS_ADMIN")

📊 Metadata

CVE ID: CVE-2025-38499

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 (2.6th percentile)

Published: August 11, 2025

Last Updated: January 7, 2026

🔗 References