CVE-2020-0435 in Android
Summary
by MITRE
In inline_data_addr of f2fs.h, there is a possible out of bounds write due to an integer overflow. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-133762747
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Analysis
by VulDB Data Team • 09/18/2020
The vulnerability identified as CVE-2020-0435 resides within the F2FS (Flash-Friendly File System) implementation in the Android kernel, specifically within the inline_data_addr function located in f2fs.h. This flaw represents a critical security weakness that manifests as an integer overflow condition leading to potential out-of-bounds write operations. The vulnerability affects Android kernel versions and is catalogued under Android ID A-133762747, highlighting its significance within the mobile operating system ecosystem.
The technical root cause of this vulnerability stems from improper integer overflow handling within the inline_data_addr function which processes file system data structures. When the system processes certain file operations involving inline data storage, the integer arithmetic calculations fail to properly validate overflow conditions. This allows malicious actors to manipulate input parameters that control data address calculations, ultimately enabling them to write data beyond the intended memory boundaries. The flaw operates at the kernel level where memory management and file system operations intersect, making it particularly dangerous for privilege escalation scenarios.
The operational impact of CVE-2020-0435 extends beyond simple data corruption, as it provides a pathway for local privilege escalation attacks. An attacker with system execution privileges can exploit this vulnerability to gain elevated privileges on the affected Android device. The vulnerability does not require user interaction for exploitation, making it particularly concerning as it can be triggered automatically during normal system operations or through crafted file system operations. The integer overflow condition creates a scenario where memory corruption can occur in critical kernel data structures, potentially leading to arbitrary code execution or system instability.
From a cybersecurity perspective, this vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and maps to ATT&CK technique T1068, which covers 'Local Privilege Escalation'. The attack surface is particularly relevant for Android devices where kernel-level vulnerabilities can be exploited to gain root access. The vulnerability demonstrates the importance of proper integer overflow checking in kernel code, especially when dealing with memory address calculations and file system operations. Security practitioners should note that this flaw represents a classic example of how seemingly minor arithmetic operations can lead to critical security implications when proper validation mechanisms are absent.
Mitigation strategies for CVE-2020-0435 should focus on immediate kernel updates and patches provided by Android security teams. Organizations should prioritize applying the relevant security patches that address the integer overflow condition in the F2FS implementation. Additionally, system administrators should implement monitoring for unusual file system operations that might indicate exploitation attempts. The vulnerability underscores the necessity of comprehensive code review processes for kernel-level components, particularly focusing on integer arithmetic validation and memory boundary checks. Regular security assessments of file system implementations and kernel modules should be conducted to identify similar vulnerabilities before they can be exploited in the wild.