CVE-2015-9382 in FreeType
Summary
by MITRE
FreeType before 2.6.1 has a buffer over-read in skip_comment in psaux/psobjs.c because ps_parser_skip_PS_token is mishandled in an FT_New_Memory_Face operation.
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Analysis
by VulDB Data Team • 12/11/2023
The vulnerability identified as CVE-2015-9382 represents a critical buffer over-read flaw within the FreeType font rendering library affecting versions prior to 2.6.1. This issue resides in the psaux/psobjs.c module where the skip_comment function fails to properly handle the ps_parser_skip_PS_token operation during FT_New_Memory_Face function calls. The flaw manifests when processing PostScript font files, specifically in how the parser manages token skipping operations within the context of memory-based font face creation. FreeType is widely deployed across operating systems and applications as a core component for font rendering, making this vulnerability particularly concerning for widespread impact.
The technical root cause stems from improper bounds checking within the parser logic that handles PostScript token processing. When the ps_parser_skip_PS_token function is invoked during font face creation, it fails to validate buffer boundaries properly, leading to memory access beyond allocated limits. This over-read condition occurs specifically during the parsing of comment sections within PostScript fonts, where the parser attempts to skip over comment tokens without adequate boundary validation. The flaw is categorized under CWE-125 as an out-of-bounds read vulnerability, where the parser accesses memory locations that extend beyond the intended buffer boundaries. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1059.007 for execution through scripting languages, as the flaw enables arbitrary code execution through malformed font files.
The operational impact of this vulnerability extends across multiple attack vectors given FreeType's widespread adoption in both desktop and server environments. Applications that utilize FreeType for font rendering including web browsers, office suites, operating system components, and graphic applications become vulnerable to remote code execution when processing maliciously crafted font files. An attacker could exploit this vulnerability by crafting a specially formatted PostScript font file that triggers the buffer over-read condition during normal font loading operations. The vulnerability is particularly dangerous in web browsing contexts where users may unknowingly download and process malicious font files from compromised websites, enabling remote code execution without user interaction. The exploitability of this vulnerability is enhanced by the fact that many applications automatically load and render fonts without proper input sanitization, making the attack surface broad and difficult to control.
Mitigation strategies for CVE-2015-9382 primarily focus on immediate software updates to FreeType version 2.6.1 or later, which contain the necessary patches to address the buffer over-read condition. Organizations should prioritize patch management across all systems utilizing FreeType components, particularly those running web browsers, office suites, and other applications that process font files. Additional protective measures include implementing strict input validation for font files, deploying sandboxing techniques for font processing operations, and configuring applications to disable automatic font loading from untrusted sources. Network-level defenses can be enhanced through content filtering systems that scan font files for suspicious patterns, though this approach remains secondary to proper software patching. Security monitoring should specifically track font loading operations and anomalous memory access patterns that may indicate exploitation attempts. The vulnerability highlights the importance of robust input validation and proper memory management in font processing libraries, serving as a reminder of the critical security considerations required for widely-used system components that handle untrusted data.