Overview
CVE-2021-26383 is a high-risk vulnerability found in the Trusted Execution Environment (TEE) of Advanced Micro Devices (AMD). This security flaw could potentially allow an attacker with a compromised userspace to invoke a command with malformed arguments. This could result in out-of-bounds memory access, leading to possible loss of system integrity or data availability. It is essential to understand and mitigate this vulnerability as it can cause serious disruptions to system operations and compromise sensitive data.
Vulnerability Summary
CVE ID: CVE-2021-26383
Severity: High (7.9 CVSS Severity Score)
Attack Vector: Local
Privileges Required: Low
User Interaction: None
Impact: Potential system compromise or data leakage
Affected Products
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Product | Affected Versions
AMD TEE | All versions prior to vendor patch
How the Exploit Works
In the case of CVE-2021-26383, an attacker who has gained access to a local userspace can exploit the vulnerability by invoking a command with malformed arguments. The insufficient bounds checking in the AMD TEE allows these malformed arguments to access memory out of the allocated bounds. This results in an illegal memory access which can lead to unpredictable system behavior, potentially allowing the attacker to compromise the system or leak data.
Conceptual Example Code
The following is a conceptual example of how the vulnerability might be exploited. Note, this is a simplified representation and actual exploit code may be more complex:
# Attacker has access to the local userspace
$ ./exploit-program --malformed-argumentIn this example, it’s assumed that the attacker has already compromised the userspace and is able to execute arbitrary commands. The `exploit-program` represents any program running in the AMD TEE, and `–malformed-argument` is an argument that can cause out-of-bounds memory access due to insufficient bounds checking.
Mitigation Guidance
The primary mitigation for this vulnerability is to apply the vendor patch provided by AMD. This patch corrects the bounds checking issue, preventing the potential for out-of-bounds memory access.
If immediate patching is not possible, a temporary mitigation can be implementing a Web Application Firewall (WAF) or an Intrusion Detection System (IDS). These security measures can help detect and block attempts to exploit this vulnerability. However, they should be considered a temporary solution until the vendor patch can be applied.
Please note, the effectiveness of WAFs and IDSs as a mitigation for this vulnerability depends on accurately identifying and blocking exploit attempts, which might not always be possible. Therefore, applying the vendor patch remains the most reliable solution.
