CVE-2019-20540 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with N(7.x), O(8.x), and P(9.0) (Exynos chipsets) software. There is a buffer over-read and possible information leak in the core touch screen driver. The Samsung ID is SVE-2019-14942 (November 2019).
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Analysis
by VulDB Data Team • 10/04/2020
This vulnerability exists within the touchscreen driver component of Samsung mobile devices running Android versions 7.x, 8.x, and 9.0, specifically affecting devices with Exynos chipsets. The issue manifests as a buffer over-read condition that occurs when processing touchscreen input data, potentially leading to information disclosure through memory access violations. The vulnerability was identified by Samsung's security team and assigned the internal identifier SVE-2019-14942, with the public disclosure occurring in November 2019. This type of flaw represents a critical security concern as it could allow attackers to extract sensitive data from the device's memory through carefully crafted touchscreen input sequences.
The technical implementation of this vulnerability stems from improper bounds checking within the touchscreen driver's data processing routines. When the driver receives touchscreen input events, it fails to validate the size of incoming data buffers before attempting to read from them. This buffer over-read condition occurs because the driver does not properly enforce the maximum buffer limits, allowing subsequent memory reads to access data beyond the allocated buffer boundaries. The flaw is classified as a CWE-125: Out-of-bounds Read vulnerability, which falls under the broader category of memory safety issues. The Exynos chipset architecture's touchscreen driver implementation contains a specific code path where input data structures are processed without adequate validation, creating an exploitable condition that could be leveraged by malicious actors.
The operational impact of this vulnerability extends beyond simple information disclosure, as it could potentially enable more sophisticated attacks through information leakage. An attacker could exploit this condition to extract sensitive information from the device's memory, including kernel memory contents, which might contain credentials, encryption keys, or other confidential data. The vulnerability affects a significant number of Samsung devices, particularly those in the Samsung Galaxy S8, S9, Note 8, and Note 9 series that utilize Exynos chipsets. The attack surface is relatively narrow as it requires physical access to the device or a way to inject malicious touchscreen input, but the potential for privilege escalation exists if combined with other vulnerabilities. This weakness aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, as it provides a potential foothold for attackers to gain deeper system access.
Mitigation strategies for this vulnerability primarily involve applying the official security patches released by Samsung for affected Android versions. Users should ensure their devices receive updates through official channels, particularly the November 2019 security patches that specifically address this issue. Device manufacturers should implement proper bounds checking in all driver components and conduct thorough code reviews to prevent similar buffer over-read conditions. The vulnerability highlights the importance of secure coding practices in embedded systems and driver development, particularly around memory management and input validation. Organizations should monitor for similar vulnerabilities in their device fleets and implement device management policies that enforce timely security updates. Additionally, security researchers should consider this vulnerability when analyzing mobile device security, as it demonstrates how seemingly benign input processing can create critical information disclosure conditions. The fix typically involves implementing proper buffer size validation and ensuring that all data processing operations within the touchscreen driver include adequate bounds checking mechanisms to prevent unauthorized memory access.