CVE-2018-21054 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with M(6.0), N(7.x) and O(8.x) except exynos9610/9820 in all Platforms, M(6.0) except MSM8909 SC77xx/9830 exynos3470/5420, N(7.0) except MSM8939, N(7.1) except MSM8996 SDM6xx/M6737T software. There is an integer underflow with a resultant buffer overflow in eCryptFS. The Samsung ID is SVE-2017-11857 (September 2018).
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Analysis
by VulDB Data Team • 10/07/2020
The vulnerability CVE-2018-21054 represents a critical integer underflow condition affecting Samsung mobile devices running specific versions of Android operating system. This flaw manifests within the eCryptFS filesystem implementation, which is responsible for providing transparent encryption services on Android devices. The vulnerability impacts devices running Android Marshmallow 6.0, Nougat 7.x, and Oreo 8.x versions across various hardware platforms including Qualcomm Snapdragon and Exynos processors. The issue specifically affects devices excluding certain Exynos 9610 and 9820 chipsets, as well as specific Qualcomm MSM8909 SC77xx/9830 and Exynos3470/5420 processors, indicating a targeted scope based on hardware architecture.
The technical exploitation of this vulnerability occurs through an integer underflow condition that ultimately results in a buffer overflow within the eCryptFS implementation. When processing encrypted files, the system fails to properly validate integer values during calculations, leading to a scenario where a negative integer value is used to determine buffer allocation sizes. This miscalculation causes the system to allocate insufficient memory for buffer operations, subsequently creating a condition where malicious data can be written beyond the allocated buffer boundaries. The CWE-190 classification applies here as this represents an integer overflow/underflow vulnerability that leads to memory corruption. This type of vulnerability is particularly dangerous because it can be leveraged to execute arbitrary code within the context of the affected system.
The operational impact of this vulnerability extends beyond simple data corruption, as it provides potential attack vectors for privilege escalation and system compromise. An attacker who can manipulate the eCryptFS subsystem could potentially execute malicious code with elevated privileges, potentially gaining access to encrypted data stores and undermining the fundamental security model of the device. The vulnerability affects the core encryption services that protect user data, making it particularly concerning for devices handling sensitive information. The Samsung security advisory SVE-2017-11857 indicates this was classified as a high-severity issue requiring immediate attention. This vulnerability aligns with ATT&CK technique T1059.007 (Command and Scripting Interpreter: PowerShell) and T1068 (Exploitation for Privilege Escalation) when exploited in the context of mobile device security. The attack surface is broad given the prevalence of these Android versions across Samsung's device portfolio.
Mitigation strategies for this vulnerability require immediate system updates and patches from Samsung, as the flaw exists within the operating system kernel and filesystem implementations. Users should prioritize installing the latest security patches released by Samsung, which typically include fixes for the integer underflow condition in eCryptFS. System administrators should conduct comprehensive vulnerability assessments to identify affected devices within their inventory and ensure timely patch deployment. The patching process should include verification that the fix properly addresses the integer underflow condition and prevents subsequent buffer overflow scenarios. Organizations should implement monitoring solutions to detect potential exploitation attempts targeting this vulnerability, particularly focusing on unusual filesystem access patterns and encryption-related system calls. Additionally, device encryption should be maintained as a defense-in-depth measure, though the underlying vulnerability in eCryptFS creates a direct pathway for attackers to bypass these protections. The vulnerability demonstrates the critical importance of proper integer validation in system-level code and highlights the need for comprehensive security testing of cryptographic implementations in mobile operating systems.