CVE-2018-0488 in ARM mbed TLS
Summary
by MITRE
ARM mbed TLS before 1.3.22, before 2.1.10, and before 2.7.0, when the truncated HMAC extension and CBC are used, allows remote attackers to execute arbitrary code or cause a denial of service (heap corruption) via a crafted application packet within a TLS or DTLS session.
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Analysis
by VulDB Data Team • 02/06/2023
The vulnerability identified as CVE-2018-0488 represents a critical heap corruption issue within the ARM mbed TLS cryptographic library that affects multiple version ranges including 1.3.21 and earlier, 2.1.9 and earlier, and 2.6.9 and earlier. This flaw specifically manifests when the truncated HMAC extension is combined with CBC (Cipher Block Chaining) mode encryption within TLS or DTLS sessions, creating a dangerous combination that can be exploited by remote attackers to achieve arbitrary code execution or cause denial of service conditions. The vulnerability stems from improper handling of packet processing when these specific cryptographic extensions are enabled, allowing attackers to craft malicious application packets that trigger memory corruption.
The technical root cause of this vulnerability lies in the improper validation and processing of HMAC truncated values within the context of CBC encryption. When mbed TLS processes TLS or DTLS packets with truncated HMAC enabled and CBC mode active, the library fails to properly validate the length and structure of the HMAC values in relation to the encrypted data. This oversight creates a scenario where an attacker can manipulate the packet structure to cause heap memory corruption during the HMAC verification process. The vulnerability is particularly dangerous because it can be exploited remotely without requiring authentication, making it a significant threat to any system utilizing affected versions of the mbed TLS library in TLS or DTLS implementations.
From an operational impact perspective, this vulnerability affects a wide range of systems that depend on mbed TLS for secure communications, including embedded devices, IoT appliances, network infrastructure, and application servers that implement TLS or DTLS protocols. The potential for arbitrary code execution means that successful exploitation could allow attackers to gain full control over affected systems, while the denial of service component can be used to disrupt services and create availability issues. The vulnerability is particularly concerning in environments where embedded systems or resource-constrained devices are deployed, as these systems often cannot be easily patched or updated, leaving them permanently exposed to exploitation.
Security professionals should consider this vulnerability in the context of CWE-121, which addresses heap-based buffer overflow conditions, and the ATT&CK framework's T1059.007 technique for command and script injection. The attack surface is extensive given mbed TLS's widespread adoption across numerous platforms and applications. Organizations should prioritize immediate patching of all affected versions to prevent exploitation, while implementing network monitoring to detect potential exploitation attempts. Additionally, administrators should consider disabling the truncated HMAC extension and CBC mode combinations in configurations where these features are not strictly required, as a temporary mitigation measure until full patches are deployed. The vulnerability highlights the critical importance of proper cryptographic library maintenance and the potential risks associated with enabling experimental or less commonly used cryptographic extensions without thorough security validation.