CVE-2018-21058 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with N(7.0), O(8.0) (exynos7420 or Exynos 8890/8996 chipsets) software. Cache attacks can occur against the Keymaster AES-GCM implementation because T-Tables are used; the Cryptography Extension (CE) is not used. The Samsung ID is SVE-2018-12761 (September 2018).
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Analysis
by VulDB Data Team • 10/07/2020
This vulnerability represents a critical cryptographic weakness in Samsung's implementation of AES-GCM encryption on specific mobile devices running Android versions 7.0 and 8.0. The flaw specifically affects devices equipped with Exynos 7420, 8890, or 8996 chipsets, where the Keymaster cryptographic implementation fails to utilize the hardware-based Cryptography Extension (CE) that would normally provide protection against cache-based side-channel attacks. The vulnerability stems from the use of T-Tables during AES-GCM operations, which creates predictable cache access patterns that can be exploited by attackers to recover cryptographic keys through cache timing attacks.
The technical implementation flaw manifests in the cryptographic library's failure to leverage hardware acceleration features that would normally mitigate such attacks. When T-Tables are used instead of the more secure hardware-based cryptography extension, the implementation becomes vulnerable to cache timing attacks that can extract sensitive key material from the device's memory. This weakness directly violates the principles outlined in CWE-310, which addresses cryptographic weaknesses related to improper implementation of cryptographic functions and lack of protection against side-channel attacks. The vulnerability operates at the intersection of cryptographic implementation security and hardware security features, making it particularly dangerous as it exploits the gap between software cryptographic implementation and hardware security capabilities.
The operational impact of this vulnerability extends beyond simple data compromise, as it enables sophisticated attackers to perform cache-based key recovery attacks that can decrypt sensitive information processed by the device. Attackers can potentially extract encryption keys used for secure communications, data storage, and authentication processes, thereby compromising the confidentiality and integrity of data protected by AES-GCM encryption. The vulnerability affects devices that rely on Samsung's proprietary cryptographic implementations, creating a widespread risk across multiple device models and software versions that share the same hardware and software architecture. This represents a significant concern for enterprise security and mobile device management, as it undermines the fundamental security guarantees that users expect from their mobile devices.
Mitigation strategies for this vulnerability require a multi-layered approach that addresses both the immediate implementation flaw and broader security architecture concerns. Device manufacturers should prioritize updating cryptographic implementations to utilize hardware-based cryptography extensions when available, as recommended by the NIST SP 800-57 standard for cryptographic key management. Organizations should implement additional security controls such as monitoring for unusual cache access patterns and ensuring that cryptographic operations are performed in secure enclaves when possible. The vulnerability also highlights the importance of proper cryptographic implementation practices and adherence to security frameworks such as those outlined in the MITRE ATT&CK framework, specifically targeting the 'Credential Access' and 'Defense Evasion' tactics that could be leveraged through such cache-based attacks. Security teams should also consider deploying device-level protections and monitoring solutions that can detect and prevent exploitation attempts targeting cryptographic implementations.