CVE-2017-11573 in FontForge
Summary
by MITRE
FontForge 20161012 is vulnerable to a buffer over-read in ValidatePostScriptFontName (parsettf.c) resulting in DoS or code execution via a crafted otf file.
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Analysis
by VulDB Data Team • 12/13/2022
FontForge version 20161012 contains a critical buffer over-read vulnerability in the ValidatePostScriptFontName function within the parsettf.c source file that presents significant security implications for systems processing font files. This vulnerability arises from insufficient input validation when parsing OpenType font files, specifically when handling PostScript font names that exceed predetermined buffer boundaries. The flaw allows attackers to craft malicious otf files that trigger memory access violations during font validation processes, creating potential pathways for denial of service conditions or arbitrary code execution within the application context.
The technical implementation of this vulnerability stems from improper bounds checking during the parsing of font metadata, particularly within the PostScript name table processing logic. When FontForge encounters an otf file containing a specially crafted PostScript font name that exceeds the allocated buffer size, the validation routine continues reading beyond the intended memory boundaries, potentially accessing invalid memory locations or triggering segmentation faults. This over-read condition can be exploited by adversaries who construct font files with malformed name records that cause the application to behave unpredictably during processing.
The operational impact of CVE-2017-11573 extends beyond simple denial of service scenarios to encompass potential remote code execution capabilities that align with attack patterns documented in the ATT&CK framework under software supply chain compromise and malicious file execution techniques. Systems that automatically process or render font files, including web browsers, document viewers, and design applications, could become vulnerable to exploitation when encountering maliciously crafted font data. The vulnerability particularly affects environments where FontForge is used for font validation or conversion tasks, as well as any application that relies on FontForge's font parsing capabilities.
Mitigation strategies for this vulnerability should prioritize immediate patching of FontForge installations to versions that address the buffer over-read condition through proper input validation and memory boundary checks. Security practitioners should implement defensive measures such as font file validation prior to processing, sandboxing font parsing operations, and monitoring for anomalous memory access patterns during font processing operations. The vulnerability demonstrates characteristics consistent with CWE-121, heap-based buffer overflow, and CWE-125, out-of-bounds read, making it particularly susceptible to exploitation through carefully crafted input files that manipulate memory access patterns during font validation processes. Organizations should also consider implementing file type restrictions and automated scanning for potentially malicious font files in their security monitoring protocols to prevent exploitation attempts.