CVE-2021-44733
📋 TL;DR
This CVE describes a use-after-free vulnerability in the TEE subsystem of the Linux kernel caused by a race condition in tee_shm_get_from_id. Attackers could potentially exploit this to execute arbitrary code or cause denial of service. Systems running Linux kernel versions up to 5.15.11 with TEE functionality enabled are affected.
💻 Affected Systems
- Linux kernel
📦 What is this software?
Fedora by Fedoraproject
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 to kernel-level code execution, potentially leading to full system compromise.
Likely Case
Kernel panic or system crash causing denial of service.
If Mitigated
Limited impact if TEE subsystem is not used or access is restricted to trusted users.
🎯 Exploit Status
Exploitation requires local access and race condition triggering, making reliable exploitation challenging.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel 5.15.12 and later
Vendor Advisory: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=dfd0743f1d9ea76931510ed150334d571fbab49d
Restart Required: Yes
Instructions:
1. Update Linux kernel to version 5.15.12 or later. 2. Reboot system to load new kernel. 3. Verify kernel version with 'uname -r'.
🔧 Temporary Workarounds
Disable TEE subsystem
linuxRemove or disable the TEE subsystem if not required
modprobe -r optee
echo 'blacklist optee' >> /etc/modprobe.d/blacklist.conf
🧯 If You Can't Patch
- Restrict local user access to systems with TEE enabled
- Implement strict privilege separation and limit users who can access TEE functionality
🔍 How to Verify
Check if Vulnerable:
Check kernel version with 'uname -r' and verify if TEE modules are loaded with 'lsmod | grep tee'Check Version:
uname -rVerify Fix Applied:
Verify kernel version is 5.15.12 or later with 'uname -r'📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- System crash dumps
- Unexpected TEE subsystem errors
Network Indicators:
- None - local exploitation only
SIEM Query:
source="kernel" AND ("panic" OR "Oops" OR "use-after-free")🔗 References
- https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=dfd0743f1d9ea76931510ed150334d571fbab49d
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/drivers/tee/tee_shm.c
- https://github.com/pjlantz/optee-qemu/blob/main/README.md
- https://lists.debian.org/debian-lts-announce/2022/03/msg00012.html
- https://lore.kernel.org/lkml/20211215092501.1861229-1-jens.wiklander%40linaro.org/
- https://security.netapp.com/advisory/ntap-20220114-0003/
- https://www.debian.org/security/2022/dsa-5096
- https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=dfd0743f1d9ea76931510ed150334d571fbab49d
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/drivers/tee/tee_shm.c
- https://github.com/pjlantz/optee-qemu/blob/main/README.md
- https://lists.debian.org/debian-lts-announce/2022/03/msg00012.html
- https://lore.kernel.org/lkml/20211215092501.1861229-1-jens.wiklander%40linaro.org/
- https://security.netapp.com/advisory/ntap-20220114-0003/
- https://www.debian.org/security/2022/dsa-5096
