CVE-2025-37899: Linux Kernel ksmbd Use-After-Free Flaw

CVE-2025-37899 Overview

In the Linux kernel, the ksmbd subsystem has a use-after-free vulnerability during session logoff. The sess->user object can be in use by another thread when a session setup request attempts to bind to the session being freed.

Critical Impact
This flaw can lead to system instability and potentially allow local attackers to execute arbitrary code.

Affected Products

Not Available
Not Available
Not Available

Discovery Timeline

Not Available - Vulnerability discovered by Not Available
Not Available - Responsible disclosure to Not Available
Not Available - CVE CVE-2025-37899 assigned
Not Available - Not Available releases security patch
2025-05-20 - CVE CVE-2025-37899 published to NVD
2025-05-24 - Last updated in NVD database

Technical Details for CVE-2025-37899

Vulnerability Analysis

This vulnerability occurs in the ksmbd subsystem of the Linux kernel. The sess->user object may be accessed by another thread during a session logoff process, triggering use-after-free conditions.

Root Cause

The root cause is concurrent access to the sess->user object by multiple threads during session logoff.

Attack Vector

Unknown

// Example exploitation code (sanitized)
struct session *sess = find_session();
if (sess) {
    // Incorrect handling of sess->user may trigger use-after-free
    bind_to_session(sess);
    // ...
}

Detection Methods for CVE-2025-37899

Indicators of Compromise

System crashes or kernel panic traces involving ksmbd
Unusual logoff operation logs
Resource exhaustion warnings

Detection Strategies

Utilize kernel monitoring tools to trace session lifecycle events. Look for signs of concurrent access errors or unexpected logoff behavior.

Monitoring Recommendations

Kernel logs should be monitored closely for anomalies in the ksmbd subsystem using enhanced logging levels.

How to Mitigate CVE-2025-37899

Immediate Actions Required

Apply kernel updates from the official repositories
Isolate vulnerable systems if updates can't be applied immediately
Monitor for any exploitation attempts actively

Patch Information

Please refer to the official Linux kernel repositories and updates for patches. Links provided in the external references include patches issued for resolving this vulnerability.

Workarounds

If immediate patching is not feasible, consider restricting access to systems running vulnerable kernels to trusted networks only.

bash

# Configuration example
ufw enable
ufw allow from 192.168.1.0/24 to any port 445