CVE-2021-47517
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's ethtool subsystem. It allows local attackers to execute operations on network devices during unregistration, potentially leading to kernel crashes or arbitrary code execution. Systems running vulnerable Linux kernel versions with ethtool access are affected.
💻 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 →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
Kernel panic, system crash, or potential arbitrary code execution with kernel privileges leading to complete system compromise.
Likely Case
Kernel crash or denial of service causing system instability and downtime.
If Mitigated
Limited impact due to requirement of local access and specific timing conditions.
🎯 Exploit Status
Exploitation requires local access and specific conditions during network interface changes.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits: 7c26da3be1e9843a15b5318f90db8a564479d2ac, cfd719f04267108f5f5bf802b9d7de69e99a99f9, dde91ccfa25fd58f64c397d91b81a4b393100ffa
Vendor Advisory: https://git.kernel.org/stable/c/7c26da3be1e9843a15b5318f90db8a564479d2ac
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. Check your distribution's security advisories for specific patched versions. 3. Reboot the system after kernel update.
🔧 Temporary Workarounds
Restrict ethtool access
linuxLimit access to ethtool command to prevent exploitation
chmod 750 /sbin/ethtool
setcap -r /sbin/ethtool
Use SELinux/AppArmor
linuxImplement mandatory access control to restrict ethtool operations
🧯 If You Can't Patch
- Restrict local user access to systems with vulnerable kernels
- Monitor for unusual ethtool usage patterns and network interface changes
🔍 How to Verify
Check if Vulnerable:
Check kernel version and compare with distribution's security advisories. Vulnerable if running kernel before fix commits.Check Version:
uname -rVerify Fix Applied:
Verify kernel version is updated to include the fix commits. Check with: uname -r and compare with patched versions from your distribution.📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- KASAN reports of use-after-free in ethtool operations
- Unexpected network interface changes
Network Indicators:
- Sudden network interface disappearance or errors
SIEM Query:
Process execution: ethtool with suspicious timing around network interface changes🔗 References
- https://git.kernel.org/stable/c/7c26da3be1e9843a15b5318f90db8a564479d2ac
- https://git.kernel.org/stable/c/cfd719f04267108f5f5bf802b9d7de69e99a99f9
- https://git.kernel.org/stable/c/dde91ccfa25fd58f64c397d91b81a4b393100ffa
- https://git.kernel.org/stable/c/7c26da3be1e9843a15b5318f90db8a564479d2ac
- https://git.kernel.org/stable/c/cfd719f04267108f5f5bf802b9d7de69e99a99f9
- https://git.kernel.org/stable/c/dde91ccfa25fd58f64c397d91b81a4b393100ffa
