CVE-2025-39825 – A race condition vulnerability exists in the Li... (How to Fix)

Q: What is the severity of CVE-2025-39825?

CVE-2025-39825 has a CVSS score of 4.7 (MEDIUM). A race condition vulnerability exists in the Linux kernel's SMB client implementation during rename operations. This allows concurrent file opens to interfere with rename processes, potentially causing file corruption or access issues. Systems using affected Linux kernel versions with SMB client functionality are vulnerable.

📋 TL;DR

A race condition vulnerability exists in the Linux kernel's SMB client implementation during rename operations. This allows concurrent file opens to interfere with rename processes, potentially causing file corruption or access issues. Systems using affected Linux kernel versions with SMB client functionality are vulnerable.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected versions not specified in CVE; check kernel commit history for exact ranges

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems using SMB client functionality; requires concurrent file operations during rename.

📦 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

File corruption, denial of service through file access disruption, or privilege escalation if combined with other vulnerabilities.

🟠

Likely Case

File access failures, application crashes, or temporary denial of service for specific files during rename operations.

🟢

If Mitigated

Minimal impact with proper access controls and monitoring; isolated file access issues at most.

🌐 Internet-Facing: LOW - Requires SMB access and specific timing conditions; not directly exploitable over internet without SMB exposure.

🏢 Internal Only: MEDIUM - Internal SMB clients could experience file access issues during rename operations with concurrent access.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires precise timing and concurrent file operations; not trivial to exploit reliably.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 24b9ed739c8c5b464d983e12cf308982f3ae93c2, 289f945acb20b9b54fe4d13895e44aa58965ddb2, c9991af5e09924f6f3b3e6996a5e09f9504b4358, c9e7de284da0be5b44dbe79d71573f9f7f9b144c, d84291fc7453df7881a970716f8256273aca5747

Vendor Advisory: https://git.kernel.org/stable/c/24b9ed739c8c5b464d983e12cf308982f3ae93c2

Restart Required: Yes

Instructions:

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

🔧 Temporary Workarounds

Disable SMB client usage

all

Avoid using SMB client functionality for file operations

Implement file access coordination

all

Use file locking or coordination mechanisms to prevent concurrent opens during rename operations

🧯 If You Can't Patch

Monitor SMB client logs for file access errors during rename operations
Implement strict access controls to limit concurrent file operations

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with patched commits; examine if SMB client is in use

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes the fix commits; test rename operations with concurrent SMB file access

📡 Detection & Monitoring

Log Indicators:

SMB client errors during rename operations
File access failures in application logs
Kernel messages about file handle issues

Network Indicators:

Increased SMB error responses
Unusual file operation patterns

SIEM Query:

source="kernel" AND "SMB" AND ("rename" OR "concurrent" OR "race")

📊 Metadata

CVE ID: CVE-2025-39825

CVSS v3 Score: 4.7 (MEDIUM)

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

CWE: CWE-362

EPSS Score: 0.01% exploit probability (0.6th percentile)

Published: September 16, 2025

Last Updated: January 16, 2026

🔗 References

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🔗 Related Vulnerabilities

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