CVE-2015-5874 in Watch
Summary
by MITRE
CoreText in Apple iOS before 9 and iTunes before 12.3 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted font file.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 06/19/2022
The vulnerability identified as CVE-2015-5874 represents a critical memory corruption flaw within Apple's CoreText framework that affected iOS versions prior to 9.0 and iTunes versions before 12.3. This vulnerability resides in the font processing subsystem where the CoreText engine handles font rendering and text layout operations. The flaw manifests when the system processes specially crafted font files that contain malformed or malicious data structures, leading to unpredictable behavior in the memory management system. Attackers can exploit this weakness by delivering malicious font files through various attack vectors including email attachments, web downloads, or malicious websites that automatically trigger font rendering during document or webpage display.
The technical nature of this vulnerability aligns with CWE-125, which describes out-of-bounds read conditions that can lead to memory corruption and arbitrary code execution. The CoreText framework's font parser fails to properly validate font file structures, particularly when handling font tables and metadata that define character glyphs, kerning information, and other typographic attributes. When encountering malformed font data, the parser's memory allocation and access patterns become corrupted, potentially allowing attackers to overwrite critical memory regions or execute arbitrary code within the context of the affected application. This memory corruption can occur during normal font processing operations when the system attempts to render text using the malicious font file.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to encompass full arbitrary code execution capabilities. Attackers can leverage this flaw to compromise user devices remotely, potentially gaining access to sensitive user data, personal information, and device functionality. The vulnerability is particularly dangerous because font files are commonly encountered during routine system operations, making exploitation highly likely. When a user opens a document, visits a website, or even receives an email with embedded fonts, the malicious font could trigger the vulnerability without user interaction. The attack surface includes not only direct exploitation but also potential use in supply chain attacks where malicious font files are embedded in legitimate documents or applications.
Mitigation strategies for CVE-2015-5874 require immediate system updates to the patched versions of iOS 9.0 and iTunes 12.3, which address the memory corruption issues in CoreText's font parsing routines. Organizations should implement comprehensive patch management procedures to ensure all affected systems receive updates promptly. Network administrators should consider implementing web content filtering and email scanning solutions to block suspicious font files before they reach end-user devices. The vulnerability demonstrates the importance of input validation and memory safety practices in system components that handle user-supplied data, aligning with ATT&CK technique T1059.007 for process injection and T1068 for exploit for privilege escalation. Additionally, security teams should monitor for indicators of compromise related to font file processing and implement monitoring for unusual memory access patterns or application crashes that might indicate exploitation attempts.