CVE-2016-2414 in Android
Summary
by MITRE
The Minikin library in Android 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before 2016-04-01 does not properly consider negative size values in font data, which allows remote attackers to cause a denial of service (memory corruption and reboot loop) via a crafted font, aka internal bug 26413177.
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Analysis
by VulDB Data Team • 07/12/2022
The vulnerability identified as CVE-2016-2414 resides within the Minikin font rendering library that forms a critical component of Android's text processing infrastructure. This library handles font data parsing and rendering operations across various Android versions including 5.0.x prior to 5.0.2, 5.1.x prior to 5.1.1, and Android 6.0 releases before the 2016-04-01 security update. The flaw represents a classic buffer overread condition that occurs when the library fails to properly validate font metadata, specifically negative size values that should never appear in legitimate font files. This oversight creates a path for malicious actors to craft specially designed font files that trigger memory corruption during the rendering process.
The technical exploitation of this vulnerability leverages the Minikin library's insufficient input validation mechanisms when processing font data structures. When a crafted font file containing negative size values is loaded, the library's parsing routine attempts to allocate memory or perform operations based on these invalid parameters, resulting in memory corruption. The vulnerability manifests as a denial of service condition where the system enters a reboot loop, effectively rendering the device unusable until manual intervention occurs. This behavior stems from the Android operating system's crash recovery mechanisms attempting to restart the system after detecting memory corruption, but the corrupted state persists across restart cycles.
From a cybersecurity perspective, this vulnerability aligns with CWE-129, which addresses insufficient validation of length values, and represents a significant concern for mobile device security. The attack surface is particularly wide given that Android devices commonly process fonts from various sources including web content, email attachments, and third-party applications. The vulnerability enables attackers to achieve remote code execution potential through device compromise, as demonstrated by the ATT&CK framework's T1203 technique for Exploitation for Client Execution. The memory corruption aspect creates opportunities for more sophisticated attacks beyond simple denial of service, though the primary impact remains system instability and user inconvenience.
Organizations and device manufacturers should prioritize immediate patch deployment for affected Android versions, as the vulnerability represents a critical security risk that could be exploited in targeted attacks. The remediation strategy involves updating the Minikin library components to include proper validation of font metadata, specifically ensuring that size parameters are validated against negative values before processing. System administrators should implement proactive monitoring for suspicious font file patterns and consider network-level filtering of font content from untrusted sources. Additionally, device manufacturers should enhance their font processing pipelines with additional input sanitization and robust error handling to prevent similar vulnerabilities from emerging in future releases, as this represents a fundamental flaw in the text rendering subsystem that could potentially affect other font-related components.