Introduction
Out-of-bounds memory access in trusted execution environments can undermine the isolation guarantees that modern processors rely on for protecting sensitive operations. CVE-2021-26383 exposes a critical flaw in AMD's Trusted Execution Environment (TEE) that could allow attackers with userspace compromise to escalate privileges or disrupt system integrity across a wide range of AMD platforms.
About AMD and TEE: AMD is a major semiconductor manufacturer with a global footprint in CPUs, GPUs, and embedded systems. Its TEE implementation is a hardware-backed secure enclave used in client, embedded, and graphics products to isolate sensitive operations from the main OS. The TEE is foundational for confidential computing and hardware-based security in AMD's ecosystem.
Technical Information
CVE-2021-26383 results from insufficient bounds checking in the AMD TEE. The TEE driver mediates communication between userspace and the secure enclave. If an attacker compromises userspace, they can craft and send malformed commands to the TEE driver. Due to inadequate parameter validation, these commands can trigger out-of-bounds memory access within the TEE, classified as CWE-787 (out-of-bounds write).
The vulnerability is present at the boundary where user-supplied arguments are not adequately checked before being processed by the secure environment. This can lead to corruption of TEE memory, potentially allowing privilege escalation or denial of service. The flaw is documented in AMD security bulletins for client, embedded, and graphics products. No public code snippets or proof-of-concept exploits are available.
Affected Systems and Versions
CVE-2021-26383 affects multiple AMD product lines, as documented in the following advisories:
- AMD-SB-4012: Client products (August 2025 bulletin)
- AMD-SB-5007: Embedded products (August 2025 bulletin)
- AMD-SB-6018: Graphics products (August 2025 bulletin)
Exact affected versions and configurations are detailed in the above bulletins. Users should review these documents for product-specific information.
Vendor Security History
AMD has a documented history of vulnerabilities in trusted computing components, including TEE and SEV. Notable prior issues include speculative execution attacks and memory corruption bugs. AMD typically issues detailed advisories and firmware updates, but the recurrence of critical flaws in security-sensitive areas is an ongoing concern for organizations relying on AMD platforms for confidential computing.