CVE-2021-47306
📋 TL;DR
This is a use-after-free vulnerability in the Linux kernel's FDDI network driver that allows local attackers to potentially execute arbitrary code or cause denial of service. It affects Linux systems with the FDDI driver loaded, though FDDI is a legacy networking technology rarely used today.
💻 Affected Systems
- Linux kernel
📦 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 →⚠️ Risk & Real-World Impact
Worst Case
Local privilege escalation to kernel-level code execution, potentially leading to full system compromise.
Likely Case
Kernel panic or system crash causing denial of service.
If Mitigated
No impact if FDDI driver is not loaded or system is patched.
🎯 Exploit Status
Requires local access and FDDI driver loaded. No public exploits known.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patched in Linux kernel stable versions via commits referenced in CVE
Vendor Advisory: https://git.kernel.org/stable/c/04b06716838bfc26742dbed3ae1d3697fe5317ee
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution's repositories. 2. Reboot system to load new kernel.
🔧 Temporary Workarounds
Unload FDDI driver
linuxRemove the vulnerable driver module if not needed
rmmod fddi
modprobe -r fddi
Blacklist FDDI driver
linuxPrevent FDDI driver from loading at boot
echo 'blacklist fddi' >> /etc/modprobe.d/blacklist.conf
🧯 If You Can't Patch
- Ensure FDDI driver is not loaded (check with lsmod | grep fddi)
- Restrict local user access to prevent potential exploitation
🔍 How to Verify
Check if Vulnerable:
Check if FDDI driver is loaded: lsmod | grep fddi. If loaded and kernel is unpatched, system is vulnerable.Check Version:
uname -rVerify Fix Applied:
Check kernel version is patched and FDDI driver either not loaded or updated.📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages
- System crashes related to network drivers
Network Indicators:
- Unusual local privilege escalation attempts
SIEM Query:
Process monitoring for unexpected privilege escalation from local users🔗 References
- https://git.kernel.org/stable/c/04b06716838bfc26742dbed3ae1d3697fe5317ee
- https://git.kernel.org/stable/c/bdfbb51f7a437ae8ea91317a5c133ec13adf3c47
- https://git.kernel.org/stable/c/deb7178eb940e2c5caca1b1db084a69b2e59b4c9
- https://git.kernel.org/stable/c/f33605908a9b6063525e9f68e62d739948c5fccf
- https://git.kernel.org/stable/c/04b06716838bfc26742dbed3ae1d3697fe5317ee
- https://git.kernel.org/stable/c/bdfbb51f7a437ae8ea91317a5c133ec13adf3c47
- https://git.kernel.org/stable/c/deb7178eb940e2c5caca1b1db084a69b2e59b4c9
- https://git.kernel.org/stable/c/f33605908a9b6063525e9f68e62d739948c5fccf
