CVE-2020-10941 in ARM mbed TLS
Summary
by MITRE
Arm Mbed TLS before 2.6.15 allows attackers to obtain sensitive information (an RSA private key) by measuring cache usage during an import.
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Analysis
by VulDB Data Team • 05/11/2024
The vulnerability identified as CVE-2020-10941 affects Arm Mbed TLS versions prior to 2.6.15 and represents a significant side-channel attack vector that exploits cache timing information to extract RSA private keys. This weakness falls under the category of cache-based side-channel attacks, which leverage the temporal characteristics of memory access patterns to infer sensitive cryptographic information. The attack specifically targets the RSA key import process where the implementation does not adequately protect against cache timing variations that could reveal information about the private key components.
The technical flaw manifests in the cryptographic library's handling of RSA key operations where cache usage patterns during key import operations are not properly randomized or abstracted. When an RSA private key is imported into the Mbed TLS library, the implementation performs certain operations that create predictable cache access patterns. Attackers can measure these cache usage characteristics through microarchitectural side-channel analysis to reconstruct the private key components. This vulnerability is particularly concerning because it operates at the hardware level where cache behavior is influenced by the actual data being processed, making it difficult to detect through traditional software-based security measures.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially compromise the entire cryptographic security infrastructure relying on Mbed TLS. Organizations using affected versions of the library may experience unauthorized key extraction, leading to complete compromise of encrypted communications, digital signatures, and authentication mechanisms that depend on RSA cryptography. The attack requires relatively sophisticated knowledge and access to perform cache timing measurements, but the potential consequences are severe as it can result in long-term exposure of cryptographic secrets that may be used to decrypt past communications or forge digital signatures.
Mitigation strategies for CVE-2020-10941 primarily involve upgrading to Arm Mbed TLS version 2.6.15 or later, which implements proper cache timing randomization and constant-time operations during RSA key import processes. Organizations should also consider implementing additional countermeasures such as cache isolation techniques, memory access randomization, and regular security audits of cryptographic implementations. The vulnerability aligns with CWE-310, which addresses cryptographic weakness related to side-channel attacks, and can be mapped to ATT&CK technique T1552.004 for unsecured credentials and T1005 for data from local system. Network defenders should monitor for potential exploitation attempts and ensure that all systems utilizing Mbed TLS are patched promptly to prevent attackers from leveraging this cache-based timing attack vector to compromise RSA key security.