CVE-2021-47219
📋 TL;DR
This CVE describes an out-of-bounds read vulnerability in the Linux kernel's scsi_debug driver. An attacker can cause kernel memory corruption by passing specially crafted SCSI commands, potentially leading to system crashes or information disclosure. Systems using the scsi_debug driver 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to denial of service, or potential information disclosure from kernel memory.
Likely Case
System crash or instability requiring reboot.
If Mitigated
Limited impact if scsi_debug driver is not loaded or access is restricted.
🎯 Exploit Status
Requires ability to send SCSI commands to the scsi_debug device, typically needing local access or compromised service.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits: 66523553fa62c7878fc5441dc4e82be71934eb77, 8440377e1a5644779b4c8d013aa2a917f5fc83c3, f347c26836c270199de1599c3cd466bb7747caa9
Vendor Advisory: https://git.kernel.org/stable/c/66523553fa62c7878fc5441dc4e82be71934eb77
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix. 2. Check your distribution's security advisories for specific patched versions. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Unload scsi_debug module
linuxRemove the vulnerable driver if not needed
sudo rmmod scsi_debug
Blacklist scsi_debug module
linuxPrevent scsi_debug from loading automatically
echo 'blacklist scsi_debug' | sudo tee /etc/modprobe.d/blacklist-scsi_debug.conf
🧯 If You Can't Patch
- Ensure scsi_debug module is not loaded in production systems
- Restrict access to SCSI devices to trusted users only
🔍 How to Verify
Check if Vulnerable:
Check if scsi_debug module is loaded: lsmod | grep scsi_debugCheck Version:
uname -rVerify Fix Applied:
Check kernel version against patched versions from your distribution's security advisory📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- KASAN reports for scsi_debug
- System crashes after SCSI operations
Network Indicators:
- Unusual SCSI command patterns to local devices
SIEM Query:
Process monitoring for scsi_debug module loading or SCSI command execution patterns🔗 References
- https://git.kernel.org/stable/c/66523553fa62c7878fc5441dc4e82be71934eb77
- https://git.kernel.org/stable/c/8440377e1a5644779b4c8d013aa2a917f5fc83c3
- https://git.kernel.org/stable/c/f347c26836c270199de1599c3cd466bb7747caa9
- https://git.kernel.org/stable/c/66523553fa62c7878fc5441dc4e82be71934eb77
- https://git.kernel.org/stable/c/8440377e1a5644779b4c8d013aa2a917f5fc83c3
- https://git.kernel.org/stable/c/f347c26836c270199de1599c3cd466bb7747caa9
