CVE-2017-13215 in Android
Summary
by MITRE
A elevation of privilege vulnerability in the Upstream kernel skcipher. Product: Android. Versions: Android kernel. Android ID: A-64386293. References: Upstream kernel.
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Analysis
by VulDB Data Team • 12/20/2019
The vulnerability described in CVE-2017-13215 represents a critical elevation of privilege flaw within the Android kernel's upstream cryptographic implementation, specifically affecting the skcipher subsystem. This vulnerability resides in the kernel's handling of symmetric key cipher operations and provides malicious actors with the ability to escalate their privileges from unprivileged user contexts to kernel-level access. The issue manifests through improper validation and handling of cryptographic operations within the kernel's crypto framework, creating a pathway for attackers to execute arbitrary code with the highest system privileges.
The technical root cause of this vulnerability stems from insufficient input validation and memory management within the skcipher implementation of the Linux kernel's crypto API. When processing cryptographic operations, the kernel fails to properly validate certain parameters and buffer boundaries, allowing attackers to manipulate the cryptographic subsystem through crafted inputs. This flaw falls under the category of improper input validation as classified by CWE-20, and specifically relates to CWE-121 which deals with stack-based buffer overflows. The vulnerability enables attackers to manipulate kernel memory structures and potentially overwrite critical kernel data or function pointers, thereby gaining complete control over the system's execution flow.
The operational impact of this vulnerability is severe and far-reaching within Android environments where the affected kernel components are deployed. An attacker with local access to a device can exploit this vulnerability to gain kernel-level privileges without requiring physical access or specialized hardware. This privilege escalation allows for complete system compromise, enabling attackers to modify system files, install malicious software, access all user data, and potentially create persistent backdoors. The vulnerability affects all Android versions that utilize the affected kernel components, making it particularly dangerous as it can be exploited across a wide range of devices and configurations.
Mitigation strategies for CVE-2017-13215 should focus on immediate patch deployment from the upstream kernel maintainers and Android security teams. Organizations should prioritize applying the official kernel patches that address the specific validation issues within the skcipher subsystem. Additionally, implementing runtime protections such as kernel address space layout randomization and stack canaries can help mitigate exploitation attempts. System administrators should also consider disabling unnecessary cryptographic algorithms and modules that are not required for specific device functions. The vulnerability demonstrates the importance of proper kernel crypto API implementation and highlights the need for comprehensive security testing of cryptographic subsystems. This issue aligns with ATT&CK technique T1068 which covers exploit for privilege escalation, and specifically targets the kernel-level privilege escalation capabilities that form a critical component of Android security architecture. Regular security audits of kernel components and adherence to secure coding practices are essential to prevent similar vulnerabilities from emerging in future implementations.