CVE-2025-39891

Q: What is the severity of CVE-2025-39891?

CVE-2025-39891 has a CVSS score of 7.1 (HIGH). This CVE describes an information leak vulnerability in the Linux kernel's mwifiex WiFi driver. Uninitialized memory in the chan_stats array could allow attackers to read kernel memory contents. Systems using affected mwifiex drivers are vulnerable when WiFi functionality is enabled.

7.1 HIGH

📋 TL;DR

This CVE describes an information leak vulnerability in the Linux kernel's mwifiex WiFi driver. Uninitialized memory in the chan_stats array could allow attackers to read kernel memory contents. Systems using affected mwifiex drivers are vulnerable when WiFi functionality is enabled.

💻 Affected Systems

Products:

Linux kernel with mwifiex driver

Versions: Linux kernel versions before the fix commits (specific versions vary by distribution)

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only vulnerable when mwifiex driver is loaded and WiFi functionality is used. Systems without mwifiex hardware/driver are not affected.

📦 What is this software?

Debian Linux by Debian

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Linux Kernel by Linux

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⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel memory information leak exposing sensitive data like encryption keys, passwords, or other kernel structures to unprivileged users.

🟠

Likely Case

Limited information disclosure of kernel memory contents, potentially revealing system state information or partial memory dumps.

🟢

If Mitigated

No information leak occurs; system operates normally with proper memory initialization.

🌐 Internet-Facing: LOW - Requires local access to query WiFi survey data.

🏢 Internal Only: MEDIUM - Local users or compromised applications could exploit this to gather system information.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires local access and ability to query WiFi survey data through the driver interface.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Linux kernel with commits 05daef0442d28350a1a0d6d0e2cab4a7a91df475 or later

Vendor Advisory: https://git.kernel.org/stable/c/05daef0442d28350a1a0d6d0e2cab4a7a91df475

Restart Required: Yes

Instructions:

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

🔧 Temporary Workarounds

Disable mwifiex driver

linux

Prevent loading of vulnerable driver module

echo 'blacklist mwifiex' >> /etc/modprobe.d/blacklist.conf
rmmod mwifiex

Restrict WiFi survey access

linux

Limit access to WiFi diagnostic interfaces

chmod 600 /sys/kernel/debug/ieee80211/*/survey

🧯 If You Can't Patch

Disable WiFi functionality if not required
Implement strict access controls to prevent unprivileged users from querying WiFi survey data

🔍 How to Verify

Check if Vulnerable:

Check if mwifiex module is loaded: lsmod | grep mwifiex. Check kernel version against patched versions.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes fix commit: grep -q '05daef0442d28350a1a0d6d0e2cab4a7a91df475' /proc/version

📡 Detection & Monitoring

Log Indicators:

Unusual access to WiFi survey interfaces
Multiple failed attempts to query chan_stats

Network Indicators:

Local privilege escalation attempts following information gathering

SIEM Query:

process.name:"iw" AND command_line:"survey" OR syscall.name:"ioctl" AND device:"mwifiex"

📊 Metadata

CVE ID: CVE-2025-39891

CVSS v3 Score: 7.1 (HIGH)

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

EPSS Score: 0.02% exploit probability (5.3th percentile)

Published: October 1, 2025

Last Updated: January 23, 2026

🔗 References

https://git.kernel.org/stable/c/05daef0442d28350a1a0d6d0e2cab4a7a91df475 Patch
https://git.kernel.org/stable/c/06616410a3e5e6cd1de5b7cbc668f1a7edeedad9 Patch
https://git.kernel.org/stable/c/0e20450829ca3c1dbc2db536391537c57a40fe0b Patch
https://git.kernel.org/stable/c/32c124c9c03aa755cbaf60ef7f76afd918d47659 Patch
https://git.kernel.org/stable/c/5285b7009dc1e09d5bb9e05fae82e1a807882dbc Patch
https://git.kernel.org/stable/c/9df29aa5637d94d24f7c5f054ef4feaa7b766111 Patch
https://git.kernel.org/stable/c/9eb0118b3470b4d2e4e3bbb1fc088b30c0285d65 Patch
https://git.kernel.org/stable/c/acdf26a912190fc6746e2a890d7d0338190527b4 Patch
https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html Third Party Advisory,Mailing List
https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html Third Party Advisory,Mailing List

📋 TL;DR

💻 Affected Systems

📦 What is this software?

Debian Linux by Debian

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Disable mwifiex driver

Restrict WiFi survey access

🧯 If You Can't Patch

🔍 How to Verify

Check if Vulnerable:

Check Version:

Verify Fix Applied:

📡 Detection & Monitoring

Log Indicators:

Network Indicators:

SIEM Query:

📊 Metadata

🔗 References

📤 Share & Export