CVE-2019-20571 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with O(8.x) (with TEEGRIS) software. There is type confusion in the WVDRM Trustlet, leading to arbitrary code execution. The Samsung ID is SVE-2019-14885 (September 2019).
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Analysis
by VulDB Data Team • 10/04/2020
The vulnerability CVE-2019-20571 represents a critical type confusion flaw within the WVDRM Trustlet component of Samsung's TEEGRIS security framework running on Android 8.x devices. This issue resides in the trusted execution environment where digital rights management operations are processed, making it particularly dangerous as it operates in a privileged security context separate from the main operating system. The vulnerability was identified and tracked by Samsung under the internal identifier SVE-2019-14885, highlighting its significance within the company's security assessment processes. The flaw affects devices that implement Samsung's TEEGRIS software stack, which provides hardware-based security services including secure key storage and content protection mechanisms.
The technical root cause of this vulnerability stems from improper type validation within the WVDRM Trustlet implementation, creating a type confusion scenario that allows an attacker to manipulate memory operations through crafted inputs. When the trustlet processes certain DRM-related operations, it fails to properly validate data types, enabling an attacker to construct malicious input that causes the system to interpret memory locations as different data types than intended. This type confusion directly enables arbitrary code execution capabilities, allowing malicious actors to bypass the security boundaries that separate trusted and untrusted code execution environments. The vulnerability specifically impacts the memory management and data processing routines within the trustlet's runtime environment, where the lack of proper type checking creates exploitable conditions for privilege escalation attacks.
The operational impact of CVE-2019-20571 extends beyond simple code execution, as it fundamentally undermines the security model of Samsung's TEEGRIS implementation. Attackers who successfully exploit this vulnerability can gain elevated privileges within the secure execution environment, potentially accessing protected cryptographic keys, DRM content, or other sensitive data that should remain isolated from regular application processes. This weakness creates a persistent threat vector that can be leveraged for various malicious activities including unauthorized content access, key extraction, and potential system compromise. The vulnerability's presence in the TEEGRIS framework means that successful exploitation could provide attackers with access to the same security protections that are designed to defend against such threats, effectively creating a backdoor into the device's secure processing environment.
Mitigation strategies for CVE-2019-20571 should focus on immediate firmware updates from Samsung, as the vulnerability requires changes to the TEEGRIS software stack that cannot be addressed through traditional application-level patches. Organizations and users should prioritize applying the latest security updates released by Samsung to address the underlying type confusion issue in the WVDRM Trustlet. Additionally, network monitoring should be enhanced to detect potential exploitation attempts through unusual memory access patterns or unexpected trustlet behavior. Security teams should implement runtime integrity checks and consider deploying additional endpoint protection measures that can detect anomalous behavior within the secure execution environment. The vulnerability aligns with CWE-471, which addresses the weakness of incorrect type specification in software implementations, and represents a clear violation of the principle of least privilege in trusted execution environments. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation and code execution within secure environments, potentially enabling adversaries to establish persistent access to device-level security services that should remain protected from external interference.