CVE-2018-21065 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with M(6.0), N(7.x), and O(8.x) software. There is an integer underflow in eCryptFS because of a missing size check. The Samsung ID is SVE-2017-11855 (August 2018).
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Analysis
by VulDB Data Team • 10/07/2020
The vulnerability identified as CVE-2018-21065 represents a critical integer underflow condition within the eCryptFS implementation on Samsung mobile devices running Android versions 6.0, 7.x, and 8.x. This flaw exists within the cryptographic file system layer that Samsung employs to provide transparent encryption for user data. The issue manifests when the system fails to properly validate the size of data structures during encryption operations, creating a scenario where an attacker can manipulate input parameters to cause arithmetic underflow conditions. Such vulnerabilities are particularly dangerous in mobile environments where device security is paramount for protecting sensitive user information and maintaining system integrity. The vulnerability was assigned the Samsung-specific identifier SVE-2017-11855, indicating it was internally tracked and addressed by Samsung's security team in August 2018.
The technical root cause of this vulnerability stems from inadequate input validation within the eCryptFS subsystem where size checks are missing or insufficiently implemented. When processing encrypted file operations, the system performs arithmetic operations on integer values that represent file sizes or buffer dimensions. Without proper bounds checking, an attacker can craft malicious inputs that cause these integers to underflow, potentially resulting in unexpected memory access patterns or buffer manipulation. This type of vulnerability maps directly to CWE-191 Integer Underflow (Wrap) which is classified under the broader category of CWE-190 Integer Overflow or Wrap, both of which represent common weaknesses in software implementations where integer arithmetic operations exceed their valid range without proper validation. The flaw essentially allows for controlled manipulation of memory layouts through carefully crafted inputs that trigger the underflow condition.
The operational impact of CVE-2018-21065 extends beyond simple denial of service scenarios, as it could potentially enable more sophisticated attack vectors that leverage the integer underflow for privilege escalation or data corruption. Mobile devices running affected Android versions are particularly vulnerable because they typically handle sensitive user data including personal communications, financial information, and authentication credentials through the eCryptFS layer. Attackers could exploit this vulnerability to manipulate encrypted file operations, potentially gaining access to otherwise protected data or disrupting normal device functionality. The vulnerability also represents a significant concern from an attacker perspective as it could be leveraged in combination with other exploits to create more comprehensive attack chains. From an ATT&CK framework perspective, this vulnerability could map to techniques such as T1068 Exploitation for Privilege Escalation and T1190 Exploitation of Remote Services, as it provides a potential entry point for gaining elevated privileges through local exploitation.
Mitigation strategies for this vulnerability primarily focus on software updates and patches provided by Samsung to address the specific integer underflow condition in eCryptFS. Users should immediately install available security updates from Samsung that contain fixes for this vulnerability, as the patches typically include proper size validation and bounds checking mechanisms to prevent the underflow conditions. System administrators should also implement monitoring for unusual file system operations that might indicate exploitation attempts, particularly around encryption and decryption processes. Additional protective measures include implementing proper input validation at multiple layers of the system, ensuring that all integer operations include appropriate overflow and underflow checks, and maintaining comprehensive security monitoring to detect anomalous behavior in cryptographic operations. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts, particularly in enterprise environments where mobile devices may access sensitive corporate data. The vulnerability demonstrates the critical importance of thorough input validation in cryptographic implementations and highlights the need for comprehensive security testing of mobile operating system components.