CVE-2013-4787 in Android
Summary
by MITRE
Android 1.6 Donut through 4.2 Jelly Bean does not properly check cryptographic signatures for applications, which allows attackers to execute arbitrary code via an application package file (APK) that is modified in a way that does not violate the cryptographic signature, probably involving multiple entries in a Zip file with the same name in which one entry is validated but the other entry is installed, aka Android security bug 8219321 and the "Master Key" vulnerability.
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Analysis
by VulDB Data Team • 06/11/2024
The Android operating system version 1.6 Donut through 4.2 Jelly Bean contained a critical cryptographic signature verification flaw that fundamentally compromised the security model of the platform. This vulnerability, known as the Master Key vulnerability, exploited a weakness in how Android handled cryptographic signatures for application packages. The flaw specifically affected the Zip archive processing mechanism used to validate APK files, creating a pathway for malicious actors to bypass security controls that were designed to ensure application integrity and authenticity.
The technical implementation of this vulnerability stemmed from a specific flaw in Android's Zip file processing logic where the system would accept multiple entries with identical names within a single Zip archive. When an APK file contained two entries with the same name, one entry would be cryptographically validated against the application's signature while the other entry would be silently installed without verification. This allowed attackers to modify application components while maintaining a valid signature, effectively creating a backdoor mechanism for code execution. The vulnerability was particularly insidious because it exploited the Zip file format itself rather than the cryptographic algorithms, making it extremely difficult to detect and prevent through traditional security measures.
The operational impact of this vulnerability was severe across the Android ecosystem, as it enabled attackers to install malicious applications that could execute arbitrary code with the privileges of the target application. This meant that attackers could potentially access sensitive user data, intercept communications, modify application behavior, or even escalate privileges to gain full system control. The vulnerability affected millions of devices running Android versions from 1.6 through 4.2, creating a massive attack surface that could be exploited across various device types and manufacturers. Security researchers identified this issue as a critical flaw in the Android security architecture, with the vulnerability being assigned the identifier Android security bug 8219321 and later referenced as the Master Key vulnerability due to its ability to "master" the signature verification process.
This vulnerability directly relates to CWE-310, Cryptographic Issues, as it represents a failure in cryptographic signature validation mechanisms, and connects to ATT&CK techniques including T1059 for command and script interpreter execution and T1068 for exploit for privilege escalation. The flaw demonstrated how seemingly minor implementation details in archive processing could create fundamental security weaknesses in mobile operating systems. Organizations and security professionals had to urgently update affected devices and implement additional security measures to protect against exploitation. The vulnerability highlighted the importance of comprehensive security testing and the need for robust cryptographic verification processes in mobile platforms. This issue ultimately led to significant improvements in Android's security model and prompted better practices for handling compressed archives in mobile operating systems, establishing a critical precedent for mobile security vulnerability management and response protocols.