CVE-2025-38349 – A use-after-free vulnerability in the Linux ker... (How to Fix)

Q: What is the severity of CVE-2025-38349?

CVE-2025-38349 has a CVSS score of 7.8 (HIGH). A use-after-free vulnerability in the Linux kernel's eventpoll (epoll) subsystem allows local attackers to potentially escalate privileges or crash the system. The vulnerability occurs when the kernel incorrectly handles reference counting while holding a mutex, enabling race conditions. This affects all Linux systems using vulnerable kernel versions with epoll functionality.

📋 TL;DR

A use-after-free vulnerability in the Linux kernel's eventpoll (epoll) subsystem allows local attackers to potentially escalate privileges or crash the system. The vulnerability occurs when the kernel incorrectly handles reference counting while holding a mutex, enabling race conditions. This affects all Linux systems using vulnerable kernel versions with epoll functionality.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific vulnerable versions not explicitly stated in CVE, but patches exist for stable branches. Likely affects multiple kernel versions before the fix commits.

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires epoll functionality which is commonly used. Systems with multiple concurrent epoll users are at higher risk.

📦 What is this software?

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

Local privilege escalation to root, kernel panic leading to denial of service, or arbitrary code execution in kernel context.

🟠

Likely Case

Kernel crash or system instability leading to denial of service, with potential for privilege escalation in targeted attacks.

🟢

If Mitigated

Limited to denial of service if proper kernel hardening and privilege separation are implemented.

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

🏢 Internal Only: HIGH - Local users or compromised services can exploit this to escalate privileges or crash systems.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires local access and race condition triggering. The vulnerability was discovered through code review by security researchers.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patched in kernel commits: 521e9ff0b67c66a17d6f9593dfccafaa984aae4c, 605c18698ecfa99165f36b7f59d3ed503e169814, 6dee745bd0aec9d399df674256e7b1ecdb615444, 8c2e52ebbe885c7eeaabd3b7ddcdc1246fc400d2

Vendor Advisory: https://git.kernel.org/stable/c/521e9ff0b67c66a17d6f9593dfccafaa984aae4c

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Check with your distribution for specific patched kernel packages. 3. Reboot system after kernel update.

🔧 Temporary Workarounds

Restrict local user access

linux

Limit local user accounts and monitor for suspicious activity

Disable unnecessary epoll usage

linux

Identify and disable services that heavily use epoll if not critical

🧯 If You Can't Patch

Implement strict privilege separation and limit local user access
Monitor system logs for kernel panics or unusual epoll-related activity

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with distribution security advisories. Examine if kernel contains the vulnerable code pattern in eventpoll.c

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes the fix commits or check with 'uname -r' and compare against patched versions from your distribution

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs
System crash dumps
Unexpected process terminations

SIEM Query:

source="kernel" AND ("panic" OR "Oops" OR "general protection fault")

📊 Metadata

CVE ID: CVE-2025-38349

CVSS v3 Score: 7.8 (HIGH)

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

CWE: CWE-416

EPSS Score: 0.02% exploit probability (3.5th percentile)

Published: July 18, 2025

Last Updated: November 18, 2025

🔗 References

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