CVE-2021-25470 in TEEGRIS Secure OS
Summary
by MITRE • 10/06/2021
An improper caller check logic of SMC call in TEEGRIS secure OS prior to SMR Oct-2021 Release 1 can be used to compromise TEE.
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Analysis
by VulDB Data Team • 10/10/2021
The vulnerability identified as CVE-2021-25470 represents a critical security flaw within the TEEGRIS secure operating system that affects versions prior to the SMR October 2021 Release 1. This issue stems from improper caller verification mechanisms within the Secure Monitor Call (SMC) functionality, which forms a fundamental component of the trusted execution environment architecture. The SMC mechanism serves as the primary interface between the normal world and the secure world, making it a crucial element for maintaining the integrity and confidentiality of sensitive operations. When the caller verification logic fails to properly validate the origin and authorization of SMC requests, it creates an exploitable condition that undermines the core security assumptions of the TEE framework.
The technical flaw manifests in the insufficient validation of caller credentials during SMC execution, allowing unauthorized entities to masquerade as legitimate secure world components or trusted applications. This improper caller check logic creates a pathway for privilege escalation attacks where malicious actors can execute arbitrary code within the secure environment without proper authorization. The vulnerability specifically impacts the authentication and authorization mechanisms that should prevent unauthorized access to sensitive secure world resources and operations. Attackers can exploit this weakness to bypass security boundaries that are typically enforced by the TEEGRIS OS, potentially gaining access to confidential data, cryptographic keys, or execution privileges that should remain isolated from the normal world.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the trust model of the secure operating system. Once exploited, attackers can potentially access sensitive information stored within the TEE, modify secure operations, or even establish persistent backdoors within the secure environment. This weakness affects the core security guarantees provided by the TEEGRIS OS, undermining the confidentiality, integrity, and availability of the protected secure execution environment. The vulnerability is particularly concerning because it affects the foundational secure communication channels between the normal world and secure world, potentially allowing attackers to intercept or manipulate secure transactions and data processing operations that should remain protected from unauthorized access.
Mitigation strategies for CVE-2021-25470 require immediate deployment of the SMR October 2021 Release 1 or subsequent patches that address the caller verification logic in the SMC implementation. Organizations should also implement additional monitoring and detection measures to identify potential exploitation attempts within their secure environments. The fix typically involves strengthening the authentication mechanisms within the SMC call processing, ensuring proper validation of caller identities and authorization contexts before executing secure world operations. Security teams should conduct comprehensive assessments of their TEE implementations to identify any additional vulnerabilities that may exist in similar authentication or authorization mechanisms. This vulnerability aligns with CWE-284 which addresses improper access control, and represents a significant concern from an ATT&CK perspective under privilege escalation techniques where attackers attempt to gain elevated system privileges through weaknesses in system call interfaces.