CVE-2018-0498 in ARM mbed TLS
Summary
by MITRE
ARM mbed TLS before 2.12.0, before 2.7.5, and before 2.1.14 allows local users to achieve partial plaintext recovery (for a CBC based ciphersuite) via a cache-based side-channel attack.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability identified as CVE-2018-0498 represents a significant security flaw in the ARM mbed TLS cryptographic library that affects multiple versions prior to 2.12.0, 2.7.5, and 2.1.14. This issue manifests as a cache-based side-channel attack that enables local attackers to achieve partial plaintext recovery when the library is used with CBC-based ciphersuites. The vulnerability exploits the timing variations in cache access patterns that occur during cryptographic operations, particularly affecting the implementation of cipher block chaining modes. The attack vector requires local system access, meaning an attacker must already have execution privileges on the target system, but the implications are severe as it can compromise the confidentiality of encrypted communications.
The technical flaw stems from the implementation of the cipher block chaining algorithm within the mbed TLS library where cache timing variations reveal information about the encryption process. When processing data with CBC ciphersuites, the library's cryptographic operations exhibit different cache access patterns depending on the plaintext values being processed. This cache side-channel leakage allows an attacker to infer partial information about the plaintext through careful analysis of timing variations in memory access patterns. The vulnerability specifically targets the way the library handles block cipher operations in CBC mode, where the decryption process involves multiple memory accesses that can be correlated to reveal information about the underlying data.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable more sophisticated attacks when combined with other techniques. Local attackers can leverage this weakness to gradually reconstruct sensitive data that was encrypted using CBC-based ciphersuites within the affected mbed TLS versions. The partial plaintext recovery capability means that while complete decryption is not achieved, enough information can be extracted to potentially compromise the integrity of encrypted communications, particularly in scenarios where the plaintext contains predictable elements or follows known patterns. This vulnerability affects any system or application that relies on mbed TLS for secure communications and implements CBC-based encryption.
Mitigation strategies for CVE-2018-0498 primarily involve upgrading to patched versions of the mbed TLS library where the cache timing variations have been addressed through improved implementation techniques. Organizations should prioritize updating their systems to versions 2.12.0, 2.7.5, or 2.1.14, which contain the necessary fixes to prevent cache-based side-channel attacks. Additionally, implementing constant-time cryptographic implementations where possible can help reduce the information leakage through timing variations. The fix typically involves modifying the library's internal operations to ensure that memory access patterns remain consistent regardless of the input data, thereby eliminating the side-channel information that attackers could exploit. This vulnerability aligns with CWE-203, which describes exposure of information through side channels, and relates to ATT&CK technique T1005, which covers data from local system.