CVE-2022-21505
📋 TL;DR
This vulnerability in the Linux kernel allows bypassing lockdown mode when IMA appraisal is configured with 'ima_appraise=log' boot parameter and Secure Boot is disabled. Attackers with local high-privilege access can use kexec to execute arbitrary code despite lockdown restrictions. Systems using lockdown without Secure Boot are affected.
💻 Affected Systems
- Linux Kernel
📦 What is this software?
Linux by Oracle
Linux by Oracle
Linux by Oracle
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing execution of arbitrary kernel code, bypassing all security restrictions imposed by lockdown mode, potentially leading to persistent backdoors or complete system control.
Likely Case
Privileged local attackers bypass lockdown restrictions to load and execute unauthorized kernel modules or modified system images, compromising system integrity and confidentiality.
If Mitigated
With Secure Boot enabled or proper kernel configuration, the vulnerability cannot be exploited, maintaining full lockdown protection.
🎯 Exploit Status
Requires local high-privilege access (PR:H) and specific kernel configuration. Exploitation involves using kexec system call to bypass lockdown.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel commit 543ce63b664e2c2f9533d089a4664b559c3e6b5b and later
Vendor Advisory: https://linux.oracle.com/cve/CVE-2022-21505.html
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing commit 543ce63b664e2c2f9533d089a4664b559c3e6b5b or later. 2. Reboot system to load patched kernel. 3. Verify kernel version and that patch is applied.
🔧 Temporary Workarounds
Enable Secure Boot
linuxEnable Secure Boot in BIOS/UEFI settings to prevent setting 'ima_appraise=log' parameter
Remove ima_appraise=log boot parameter
linuxRemove or change the 'ima_appraise=log' boot parameter to 'enforce' or 'fix'
Edit /etc/default/grub or bootloader configuration, remove 'ima_appraise=log' from GRUB_CMDLINE_LINUX
Run: sudo update-grub
Reboot system
🧯 If You Can't Patch
- Enable Secure Boot in system firmware if hardware supports it
- Change IMA appraisal mode from 'log' to 'enforce' or 'fix' in boot parameters
🔍 How to Verify
Check if Vulnerable:
Check if system uses lockdown: cat /sys/kernel/security/lockdown. Check boot parameters: cat /proc/cmdline | grep ima_appraise=log. Check Secure Boot status: mokutil --sb-stateCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes commit 543ce63b664e2c2f9533d089a4664b559c3e6b5b: uname -r. Check git log for commit presence.📡 Detection & Monitoring
Log Indicators:
- Kernel logs showing kexec usage while lockdown is active
- IMA appraisal mode changes in boot logs
- Unauthorized kernel module loading attempts
SIEM Query:
source="kernel" AND ("kexec" OR "lockdown bypass" OR "ima_appraise")