CVE-2025-39863
📋 TL;DR
A use-after-free vulnerability in the Linux kernel's Broadcom WiFi driver (brcmfmac) allows local attackers to potentially crash the system or execute arbitrary code. This affects Linux systems using Broadcom WiFi chipsets. Attackers need local access to exploit this vulnerability.
💻 Affected Systems
- Linux kernel with brcmfmac driver
📦 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 →⚠️ Risk & Real-World Impact
Worst Case
Local privilege escalation leading to kernel compromise and full system control
Likely Case
Kernel panic or system crash causing denial of service
If Mitigated
Limited impact due to local access requirement and exploit complexity
🎯 Exploit Status
Race condition exploitation is challenging; requires local access to trigger
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits 2f6fbc8e04ca1d1d5c560be694199f847229c625, 3e789f8475f6c857c88de5c5bf4b24b11a477dd7, 9cb83d4be0b9b697eae93d321e0da999f9cdfcfc, or f1150153c4e5940fe49ab51136343c5b4fe49d63
Vendor Advisory: https://git.kernel.org/stable/c/2f6fbc8e04ca1d1d5c560be694199f847229c625
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution's repositories. 2. Reboot system to load new kernel. 3. Verify kernel version after reboot.
🔧 Temporary Workarounds
Disable Bluetooth coexistence feature
linuxPrevent the vulnerable code path by disabling Bluetooth coexistence in WiFi driver
echo 'options brcmfmac btcoex=0' > /etc/modprobe.d/brcmfmac-btcoex.conf
rmmod brcmfmac
modprobe brcmfmac
🧯 If You Can't Patch
- Restrict local user access to prevent exploitation
- Disable WiFi or use alternative WiFi hardware if possible
🔍 How to Verify
Check if Vulnerable:
Check if system uses brcmfmac driver: lsmod | grep brcmfmac && check kernel version against patched versionsCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix commits or is newer than vulnerable versions📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages
- System crashes related to brcmfmac driver
- Use-after-free warnings in kernel logs
Network Indicators:
- None - local vulnerability only
SIEM Query:
search 'kernel: brcmfmac' OR 'kernel: use-after-free' OR 'kernel: BUG' in system logs