CVE-2021-46894
📋 TL;DR
This CVE describes a Use After Free vulnerability in the Linux kernel's uinput module that allows local attackers to escalate privileges to kernel level. It affects Huawei devices running HarmonyOS and potentially other Linux-based systems. Successful exploitation gives attackers full system control.
💻 Affected Systems
- Huawei devices with HarmonyOS
- Linux systems with vulnerable uinput module
📦 What is this software?
Emui by Huawei
Harmonyos by Huawei
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with kernel-level privileges, allowing attackers to install persistent malware, access all data, and bypass all security controls.
Likely Case
Local privilege escalation from a low-privileged user to root/kernel level, enabling lateral movement and persistence establishment.
If Mitigated
Limited impact if proper access controls restrict local user accounts and kernel hardening measures are implemented.
🎯 Exploit Status
Requires local access and knowledge of kernel exploitation techniques. No public exploit code identified in references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: HarmonyOS security updates from July 2023 onward
Vendor Advisory: https://consumer.huawei.com/en/support/bulletin/2023/7/
Restart Required: Yes
Instructions:
1. Check for available system updates on Huawei devices. 2. Apply the July 2023 security update or later. 3. Reboot the device to load the patched kernel.
🔧 Temporary Workarounds
Disable uinput module
linuxPrevent loading of the vulnerable uinput kernel module
echo 'install uinput /bin/false' >> /etc/modprobe.d/disable-uinput.conf
rmmod uinput
Restrict module loading
linuxPrevent unauthorized kernel module loading
echo 'kernel.modules_disabled=1' >> /etc/sysctl.conf
sysctl -p
🧯 If You Can't Patch
- Restrict local user access and implement strict privilege separation
- Implement kernel hardening measures like SELinux/AppArmor with strict policies
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if uinput module is loaded: lsmod | grep uinputCheck Version:
uname -r (for kernel) or check system update historyVerify Fix Applied:
Verify the security update date is July 2023 or later and uinput module version is patched📡 Detection & Monitoring
Log Indicators:
- Kernel panic or oops messages
- Unauthorized privilege escalation attempts in audit logs
- Suspicious module loading
Network Indicators:
- None - this is a local exploit
SIEM Query:
source="kernel" AND ("uinput" OR "general protection fault" OR "use after free")🔗 References
- https://consumer.huawei.com/en/support/bulletin/2023/7/
- https://device.harmonyos.com/en/docs/security/update/security-bulletins-202307-0000001587168858
- https://consumer.huawei.com/en/support/bulletin/2023/7/
- https://device.harmonyos.com/en/docs/security/update/security-bulletins-202307-0000001587168858
