CVE-2021-47541
📋 TL;DR
A use-after-free vulnerability in the Linux kernel's mlx4_en network driver allows local attackers to potentially crash the system or execute arbitrary code. This affects systems using Mellanox ConnectX-3 network cards with the mlx4_en driver loaded. Attackers need local access to exploit this vulnerability.
💻 Affected Systems
- Linux kernel with mlx4_en 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 →⚠️ Risk & Real-World Impact
Worst Case
Local privilege escalation leading to kernel compromise and full system control
Likely Case
Kernel panic causing system crash and denial of service
If Mitigated
No impact if driver not loaded or system properly patched
🎯 Exploit Status
Found via static analysis, may be difficult to trigger in practice. Requires local access and specific hardware/driver configuration.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel stable releases containing commits referenced in CVE
Vendor Advisory: https://git.kernel.org/stable/c/676dc7d9b15bf8733233a2db1ec3f9091ab34275
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version 2. Rebuild kernel if using custom build 3. Reboot system 4. Verify mlx4_en driver loads without errors
🔧 Temporary Workarounds
Disable mlx4_en module
linuxPrevent loading of vulnerable driver if not needed
echo 'blacklist mlx4_en' >> /etc/modprobe.d/blacklist.conf
rmmod mlx4_en
🧯 If You Can't Patch
- Ensure strict access controls to prevent local user exploitation
- Monitor system logs for kernel panics or driver errors
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if mlx4_en module is loaded: lsmod | grep mlx4_enCheck Version:
uname -rVerify Fix Applied:
Verify kernel version is patched and driver loads without errors in dmesg📡 Detection & Monitoring
Log Indicators:
- Kernel panics
- mlx4_en driver errors in dmesg
- Use-after-free warnings in kernel logs
Network Indicators:
- Network interface failures on Mellanox cards
SIEM Query:
search 'kernel: mlx4_en' OR 'kernel: BUG: use-after-free'🔗 References
- https://git.kernel.org/stable/c/676dc7d9b15bf8733233a2db1ec3f9091ab34275
- https://git.kernel.org/stable/c/75917372eef0dbfb290ae45474314d35f97aea18
- https://git.kernel.org/stable/c/addad7643142f500080417dd7272f49b7a185570
- https://git.kernel.org/stable/c/be12572c5ddc8ad7453bada4eec8fa46967dc757
- https://git.kernel.org/stable/c/e461a9816a1ac5b4aeb61621b817225b61e46a68
- https://git.kernel.org/stable/c/f1d43efa59f1edd3e7eca0e94559b4c6b1cd4e2b
- https://git.kernel.org/stable/c/676dc7d9b15bf8733233a2db1ec3f9091ab34275
- https://git.kernel.org/stable/c/75917372eef0dbfb290ae45474314d35f97aea18
- https://git.kernel.org/stable/c/addad7643142f500080417dd7272f49b7a185570
- https://git.kernel.org/stable/c/be12572c5ddc8ad7453bada4eec8fa46967dc757
- https://git.kernel.org/stable/c/e461a9816a1ac5b4aeb61621b817225b61e46a68
- https://git.kernel.org/stable/c/f1d43efa59f1edd3e7eca0e94559b4c6b1cd4e2b
