CVE-2015-9213 in Android
Summary
by MITRE
In Android before 2018-04-05 or earlier security patch level on Qualcomm Snapdragon Mobile and Snapdragon Wear MDM9206, MDM9607, MDM9615, MDM9625, MDM9635M, MDM9640, MDM9645, MDM9650, MDM9655, MSM8909W, SD 210/SD 212/SD 205, SD 400, SD 410/12, SD 425, SD 430, SD 450, SD 600, SD 615/16/SD 415, SD 617, SD 625, SD 650/52, SD 800, SD 808, SD 810, SD 820, SD 835, SD 845, SD 850, and SDX20, the DIAG-EFS command EFS2_DIAG_DELTREE, which is handled by the function fs_diag_deltree_handler(), is used to delete files and directories only inside the /public folder.
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Analysis
by VulDB Data Team • 01/26/2020
The vulnerability identified as CVE-2015-9213 represents a critical privilege escalation flaw in Qualcomm Snapdragon mobile platforms that affects Android devices released before the 2018-04-05 security patch level. This issue stems from improper access controls within the DIAG-EFS command implementation, specifically the EFS2_DIAG_DELTREE function that processes file deletion requests. The vulnerability resides in the fs_diag_deltree_handler() function which is designed to handle file system operations but fails to properly validate the scope of deletion operations. The flaw allows malicious actors to bypass intended restrictions that should limit file operations to the /public directory, creating a pathway for unauthorized access to critical system files and directories beyond the designated boundaries. This represents a fundamental breakdown in the principle of least privilege and access control mechanisms that should protect system integrity and user data.
The technical implementation of this vulnerability demonstrates a classic case of inadequate input validation and privilege boundary enforcement within mobile platform firmware components. The DIAG-EFS subsystem serves as a diagnostic interface that typically operates with elevated privileges to facilitate system debugging and maintenance functions. However, the fs_diag_deltree_handler() function fails to properly sanitize or validate the paths being processed, allowing attackers to manipulate the deletion operations to target directories outside the intended /public folder scope. This vulnerability is particularly concerning as it operates at the firmware level where traditional Android security mechanisms may not fully apply, making it difficult to detect and prevent through standard application-level security controls. The flaw affects a wide range of Qualcomm Snapdragon chipsets including the MDM9206, MDM9607, MDM9615, MDM9625, MDM9635M, MDM9640, MDM9645, MDM9650, MDM9655, MSM8909W, and numerous SD series processors spanning multiple generations of mobile platforms.
The operational impact of this vulnerability extends beyond simple file deletion capabilities to encompass potential system compromise and data exposure. Attackers who can exploit this vulnerability gain the ability to remove critical system files, potentially leading to device instability, boot failures, or complete system compromise. The vulnerability creates opportunities for persistent threats to remove security-related files or system components that protect against other attacks, effectively weakening the overall security posture of affected devices. Furthermore, the ability to delete files outside the intended scope opens possibilities for creating denial of service conditions by removing essential system components or for data exfiltration by deleting files that might contain sensitive information. This vulnerability aligns with CWE-284 (Improper Access Control) and represents a significant weakness in the Android security model's defense-in-depth approach, particularly concerning the boundary protection between diagnostic interfaces and system file operations.
Mitigation strategies for this vulnerability require both immediate patching and ongoing monitoring of affected systems. Device manufacturers and carriers must ensure that all affected Snapdragon-based devices receive the appropriate security patches that address the privilege escalation in the DIAG-EFS command handling. The recommended approach involves implementing proper input validation within the fs_diag_deltree_handler() function to enforce strict path validation and ensure that all file deletion operations remain confined to the designated /public directory scope. Organizations should also consider implementing additional monitoring for unusual file system activity patterns that might indicate exploitation attempts. This vulnerability demonstrates the importance of firmware-level security controls and highlights the need for comprehensive security testing of diagnostic interfaces that operate with elevated privileges. The ATT&CK framework categorizes this issue under privilege escalation techniques and may be leveraged by adversaries seeking to establish persistent access or escalate their control within compromised systems, making it essential for security teams to monitor for potential exploitation attempts.