CVE CyberSecurity Database News

CVE-2022-41804 - How Unauthorized Error Injection in Intel SGX/TDX Can Be Exploited for Local Privilege Escalation

Poster -

In late 2022, Intel disclosed a new vulnerability affecting some Intel Xeon processors, tracked as CVE-2022-41804. This bug concerns the Intel(R) Software Guard Extensions (SGX) and Intel(R) Trusted Domain Extensions (TDX), both security features designed to create trusted execution environments on modern CPUs. Despite their goal of making data more secure, this vulnerability offers a way for a privileged local attacker to increase their level of access on the system by injecting unauthorized errors.

In this post, we’ll break down what CVE-2022-41804 is, how it works, show some code snippets related to the vulnerability, reference official documentation, and explain how an attacker could exploit this issue.

What is CVE-2022-41804?

The short version: Unauthorized error injection in Intel(R) SGX or Intel(R) TDX for some Intel(R) Xeon(R) Processors may allow a privileged user to potentially escalate privilege via local access.

Official NVD page:  
https://nvd.nist.gov/vuln/detail/CVE-2022-41804

Intel advisory:  
https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00712.html

What Does it Mean?

Intel SGX provides a "secure enclave" for code and data. TDX is similar, meant for secure virtualization. Both depend on tightly controlled hardware events and error conditions to stay secure.

But on some Xeon CPUs, a privileged (but not root–think kernel module, hypervisor, or even a VM admin) user can inject certain *machine check errors* using debug or maintenance features. These errors are supposed to be tightly controlled. If misused, they can trick the processor into mishandling privileged operations—leading to possible "escalation of privilege." That means gaining higher-level access than you were meant to have.

About Error Injection

Intel processors have a mechanism to test their error-handling by artificially injecting Machine Check Architecture (MCA) errors. Normally, only system firmware (like BIOS) or certain highly privileged code can perform such injection. In affected CPUs with certain firmware and driver combinations, this control can be bypassed or loosened.

What constitutes "privileged user"?

In most cases, this is ring- code (kernel), or processes with device file access, such as /dev/mcelog or /dev/cpu/*/*, or sometimes hypervisor-level code in virtualized setups.

Exploit Scenario

Suppose you are running code as a VM guest or even as a section in a container with some elevated privileges. If you can trigger the vulnerability, you could:

Generate faulty error conditions.

- Force the processor to enter an insecure state or mis-handle enclave/TDX protections.
- Leverage that confusion to access (read/write) memory or data outside your privilege boundary.

Code Snippet Example

Disclaimer: The following is for education and research. Don't use it for unauthorized access.

Here’s a Python snippet using /dev/cpu/ via ioctl to inject an error code (simulated)

import os
import fcntl
import struct

# Constants would be defined as per kernel headers and Intel documentation
MC_INJECT_ERR = xC010AD41          # Example IOCTL code, not real

fd = os.open('/dev/cpu//msr', os.O_RDWR)

# Prepare error injection code (example - must match real MC code format)
# Let's say: bank=4, status=error_code for SGX/TDX, others 
bank = 4
status = xDEADBEEF
err_data = struct.pack('II', bank, status)

# Attempt to inject error
try:
    fcntl.ioctl(fd, MC_INJECT_ERR, err_data)
except Exception as e:
    print(f"Error: {e}")

os.close(fd)

Note:

Exploit Outline

1. Gain privileged (local) access. Either by running a kernel module, privileged process, or in a captured VM with partial admin rights.

Inject error into the SGX or TDX-managed memory region.

3. Trigger mishandling of errors in the system software, causing unintentional elevation, leak, or override of protected data.
4. Gain higher privileges—become root/admin, access protected memory, or escape virtual isolation.

In practical terms, for cloud or datacenter operators, untrusted tenants could exploit this to break out of their VM, or escalate from container to whole host.

Patch operating systems and hypervisors to include new mitigations.

- Restrict access to error injection interfaces (/dev/mcelog, msr devices).

Audit logs for suspicious error-injection behavior.

Official patch info:  
https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00712.html

References

- Intel Security Advisory SA-00712
- NVD CVE-2022-41804 entry
- SGX programming references (Intel)

Final Thoughts

CVE-2022-41804 is one more example of how complex hardware features can leak privilege, often through subtle gaps between hardware, firmware, and operating-system security. Even if you think enclave or trusted area memory is safe, keep firmware, kernel, and hypervisors up to date—and always sandbox as much as possible.

If you’re running Intel Xeon CPUs with SGX or TDX enabled in production, pay close attention to advisories like this. Local privilege escalation can lead to big trouble, especially in shared virtual environments and the cloud.

Timeline

Published on: 08/11/2023 03:15:00 UTC
Last modified on: 08/22/2023 19:16:00 UTC