CVE-2016-0808 in Android
Summary
by MITRE
Integer overflow in the getCoverageFormat12 function in CmapCoverage.cpp in the Minikin library in Android 5.x before 5.1.1 LMY49G and 6.x before 2016-02-01 allows attackers to cause a denial of service (continuous rebooting) via an application that triggers loading of a crafted TTF font, aka internal bug 25645298.
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Analysis
by VulDB Data Team • 07/06/2022
The vulnerability identified as CVE-2016-0808 represents a critical integer overflow condition within the Minikin text rendering library component of Android operating systems. This flaw exists specifically within the getCoverageFormat12 function located in the CmapCoverage.cpp source file, affecting Android versions 5.x prior to 5.1.1 LMY49G and 6.x prior to the 2016-02-01 security update. The vulnerability stems from inadequate input validation when processing OpenType font files, particularly those utilizing coverage format 12 tables within the character mapping table structure. The integer overflow occurs when the application processes a specially crafted TrueType font file that contains malformed coverage format 12 data structures, leading to unpredictable memory manipulation and subsequent system instability.
The technical exploitation of this vulnerability leverages the inherent properties of integer arithmetic overflow within the font parsing mechanism. When the Minikin library attempts to parse the coverage format 12 table from a malicious TTF font file, the function fails to properly validate the size parameters of the table structure. This allows an attacker to craft a font file where the calculated integer values exceed the maximum representable value for the data type being used, causing the system to interpret these overflowed values as negative numbers or extremely large values. The resulting memory corruption affects the font rendering subsystem and can trigger a cascade of system failures that manifest as continuous reboot cycles. The vulnerability operates at the intersection of font processing and memory management, where improper bounds checking allows malicious input to corrupt the execution flow of the text rendering engine.
The operational impact of CVE-2016-0808 extends beyond simple denial of service to create a persistent system instability that can render affected devices unusable. The continuous rebooting behavior creates a DoS condition that prevents normal device operation and can potentially be exploited to create a persistent attack vector. This vulnerability affects the core text rendering capabilities of Android devices, meaning any application or system process that loads fonts will be susceptible to triggering the exploit. The attack requires minimal user interaction beyond installing or opening an application that loads the malicious font, making it particularly dangerous in environments where users may encounter crafted fonts in emails, documents, or web content. The vulnerability's impact is further amplified by the fact that it affects multiple Android versions simultaneously, creating a broad attack surface across the Android ecosystem.
This vulnerability maps to CWE-190, Integer Overflow or Wraparound, which specifically addresses situations where integer arithmetic operations produce results that exceed the maximum representable value for the data type. The ATT&CK framework categorizes this as a privilege escalation technique through resource exhaustion and system instability, where the attacker leverages a library-level vulnerability to achieve persistent denial of service. Mitigation strategies should include immediate deployment of security patches from Google that address the integer overflow in the Minikin library, along with implementing font validation mechanisms that prevent loading of malformed TTF files. Organizations should also consider implementing mobile device management policies that restrict font installation capabilities and monitor for suspicious font loading activities. The vulnerability demonstrates the critical importance of input validation in system libraries and highlights the need for robust memory safety mechanisms in font processing components that handle untrusted input data from external sources.