CVE-2017-11569 in FontForge
Summary
by MITRE
FontForge 20161012 is vulnerable to a heap-based buffer over-read in readttfcopyrights (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 heap-based buffer over-read vulnerability in the readttfcopyrights function within the parsettf.c source file that presents significant security implications for users processing untrusted font files. This vulnerability specifically manifests when the application processes crafted open type font files that contain malformed copyright information structures. The buffer over-read occurs due to insufficient bounds checking during the parsing of TTF (TrueType Font) copyright data, allowing an attacker to manipulate memory access patterns that extend beyond allocated heap buffers. The flaw resides in the font parsing logic where the application fails to properly validate the size and structure of copyright metadata within the font file, creating a scenario where arbitrary memory locations can be accessed and potentially modified.
The technical impact of this vulnerability spans from denial of service conditions to potential remote code execution depending on the execution environment and memory layout. When a maliciously crafted OTF file is processed by FontForge, the over-read can cause the application to access memory regions that contain sensitive data or executable code, leading to unpredictable behavior including application crashes, memory corruption, or in favorable attack scenarios, arbitrary code execution. The vulnerability is particularly concerning because font files are commonly encountered in various digital workflows and can be embedded in documents, web pages, or distributed through multiple channels, making the attack surface quite broad. This issue directly maps to CWE-125: Out-of-bounds Read within the Common Weakness Enumeration framework, which categorizes it as a memory safety vulnerability that can result in information disclosure or system compromise.
The operational impact of CVE-2017-11569 extends beyond simple application instability to potentially compromise entire systems when FontForge is used in automated processing environments or by applications that rely on font parsing capabilities. Organizations using FontForge for font manipulation, design, or conversion tasks face significant risk when processing untrusted font content, as the vulnerability can be exploited through various attack vectors including email attachments, web downloads, or document processing workflows. The vulnerability affects not only end-user applications but also server-side processes that might automatically process font files, creating potential escalation paths for attackers who can leverage this flaw to gain unauthorized access to systems. From an attack perspective, this vulnerability aligns with ATT&CK technique T1203: Exploitation for Client Execution, where attackers can use malformed file content to execute arbitrary code in the context of the vulnerable application. The risk is particularly elevated in environments where FontForge is used in automated workflows or as part of content processing pipelines, where the application might automatically process font files without user intervention.
Mitigation strategies for this vulnerability primarily focus on immediate remediation through software updates to patched versions of FontForge that address the buffer over-read condition. Users should avoid processing untrusted font files whenever possible and implement strict file validation procedures before font processing operations. Network-based defenses can include implementing file type restrictions and content filtering to prevent potentially malicious font files from reaching systems that use FontForge. Additionally, organizations should consider deploying application sandboxing techniques to isolate font processing operations and limit the potential impact of successful exploitation attempts. System administrators should monitor for any signs of exploitation attempts and maintain updated threat intelligence regarding this specific vulnerability. The vulnerability serves as a reminder of the importance of proper input validation and memory safety practices in font parsing libraries, highlighting the need for comprehensive security testing of font processing components in applications that handle untrusted binary content.