CVE-2021-33097 in Crypto API Toolkit
Summary
by MITRE • 11/17/2021
Time-of-check time-of-use vulnerability in the Crypto API Toolkit for Intel(R) SGX may allow a privileged user to potentially enable escalation of privilege via network access.
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Analysis
by VulDB Data Team • 11/21/2021
The vulnerability identified as CVE-2021-33097 represents a critical time-of-check time-of-use flaw within Intel's Software Guard Extensions Crypto API Toolkit, specifically affecting the cryptographic operations handling within SGX enclaves. This vulnerability stems from improper synchronization mechanisms between the initial validation phase and the subsequent execution phase of cryptographic operations, creating a window where malicious actors can exploit temporal inconsistencies in the system's security checks. The flaw manifests when the system performs a security check at one point in time but executes the operation at a later point, allowing for potential manipulation of the system state between these critical moments.
The technical implementation of this vulnerability resides in the cryptographic toolkit's handling of sensitive operations within Intel SGX enclaves, where the system performs validation checks before executing cryptographic functions. During this validation phase, the system verifies the legitimacy of inputs and access permissions, but the subsequent execution phase does not revalidate these conditions, creating a temporal gap that adversaries can exploit. This particular weakness aligns with CWE-367, which specifically addresses Time-of-Check to Time-of-Use vulnerabilities, where the system state changes between the check and the use operations, leading to potential privilege escalation opportunities.
The operational impact of this vulnerability extends beyond traditional security boundaries, as it specifically targets the integrity of Intel SGX security enclaves where sensitive cryptographic operations are meant to remain protected from both external and internal threats. A privileged user with network access can potentially leverage this temporal inconsistency to escalate their privileges within the system, undermining the fundamental security guarantees that SGX enclaves are designed to provide. The vulnerability affects the cryptographic toolkit's ability to maintain consistent security states throughout the execution lifecycle, potentially allowing attackers to manipulate cryptographic operations and access protected resources that should remain isolated within the enclave environment.
Mitigation strategies for CVE-2021-33097 require immediate implementation of patch updates from Intel that address the synchronization issues within the Crypto API Toolkit, ensuring that validation checks remain consistent throughout the entire operation lifecycle. Organizations should implement comprehensive monitoring of enclave operations to detect potential exploitation attempts and establish strict access controls that minimize the attack surface for privileged users. The remediation process must include thorough testing of the patched toolkit to ensure that cryptographic operations maintain their integrity and that no additional temporal inconsistencies have been introduced. Security teams should also consider implementing additional layers of protection such as intrusion detection systems specifically designed to monitor for unusual enclave behavior patterns that might indicate exploitation attempts.
This vulnerability demonstrates the complex security challenges inherent in hardware-based security solutions like Intel SGX, where the interaction between software components and hardware security features creates unique attack vectors. The issue highlights the importance of proper synchronization mechanisms in security-critical systems and the potential consequences when temporal consistency is not maintained across system operations. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques that leverage temporal inconsistencies in system validation processes, potentially enabling adversaries to move laterally within secure environments where SGX enclaves are expected to provide isolation guarantees. The exploitation of such vulnerabilities requires careful consideration of the broader security architecture and may necessitate additional security controls beyond the immediate patching of the identified flaw.