CVE-2021-47101
📋 TL;DR
This vulnerability in the Linux kernel's ASIX USB Ethernet driver allows reading uninitialized memory when the asix_mdio_read() function receives less data than expected. This affects systems using ASIX USB Ethernet adapters with vulnerable kernel versions, potentially exposing sensitive kernel memory contents.
💻 Affected Systems
- Linux kernel with ASIX USB Ethernet 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
Information disclosure of kernel memory contents, potentially exposing sensitive data like cryptographic keys, process memory, or other system information to local attackers.
Likely Case
Kernel panic or system instability due to reading invalid memory addresses, leading to denial of service.
If Mitigated
Minimal impact with proper kernel hardening and memory protection features enabled.
🎯 Exploit Status
Requires local access and ability to interact with USB Ethernet device. No known public exploits at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits 8035b1a2a37a29d8c717ef84fca8fe7278bc9f03 and d259f621c85949f30cc578cac813b82bb5169f56
Vendor Advisory: https://git.kernel.org/stable/c/8035b1a2a37a29d8c717ef84fca8fe7278bc9f03
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. For distributions: Use package manager (apt/yum/dnf) to update kernel package. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable ASIX driver
linuxPrevent loading of vulnerable asix driver module
echo 'blacklist asix' >> /etc/modprobe.d/blacklist.conf
rmmod asix
Restrict USB device access
linuxPrevent unauthorized USB Ethernet device connections
usbguard generate-policy > /etc/usbguard/rules.conf
systemctl enable --now usbguard
🧯 If You Can't Patch
- Disable or blacklist the asix kernel module to prevent driver loading
- Implement strict USB device control policies to prevent unauthorized ASIX adapter connections
🔍 How to Verify
Check if Vulnerable:
Check if asix module is loaded: lsmod | grep asix AND check kernel version against distribution security advisoriesCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix commits: grep -q '8035b1a2a37a29d8c717ef84fca8fe7278bc9f03\|d259f621c85949f30cc578cac813b82bb5169f56' /proc/version_signature📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- KMSAN (Kernel Memory Sanitizer) error reports in dmesg
- USB device connection logs for ASIX adapters
Network Indicators:
- Unexpected USB Ethernet device connections
SIEM Query:
source="dmesg" AND "KMSAN" AND "asix" OR source="kernel" AND "panic" AND "asix"