CVE-2017-11577 in FontForge
Summary
by MITRE
FontForge 20161012 is vulnerable to a buffer over-read in getsid (parsettf.c) resulting in DoS or code execution via a crafted otf file.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 12/13/2022
FontForge version 20161012 contains a critical buffer over-read vulnerability in the getsid function within the parsettf.c source file that presents significant security risks to systems processing font files. This vulnerability specifically affects the parsing of OpenType font files and represents a classic buffer over-read condition where the application attempts to read data beyond the allocated memory boundaries. The flaw occurs during the processing of font metadata, particularly when handling certain font table structures that contain malformed or specially crafted data. When a maliciously constructed otf file is processed by FontForge, the getsid function fails to properly validate input boundaries, leading to memory corruption that can result in either a denial of service condition or potentially arbitrary code execution depending on the memory layout and execution context.
The technical implementation of this vulnerability stems from inadequate bounds checking within the font parsing routine. The getsid function processes font identifier information without sufficient validation of the input data length, allowing an attacker to craft an otf file containing oversized or malformed identifier fields that exceed the allocated buffer space. This over-read condition typically manifests when the application attempts to access memory locations beyond the intended buffer boundaries, potentially reading sensitive data from adjacent memory regions or causing the application to crash due to invalid memory access violations. The vulnerability is particularly concerning because font files are commonly processed by various applications across different operating systems, making the attack surface broad and potentially exploitable in multiple contexts.
The operational impact of CVE-2017-11577 extends beyond simple denial of service scenarios to include potential remote code execution capabilities that could be leveraged by attackers in targeted attacks. When exploited, this vulnerability can cause FontForge applications to crash or behave unpredictably, disrupting legitimate font processing operations. In more severe exploitation scenarios, attackers could potentially execute arbitrary code on systems running vulnerable versions of FontForge, especially when the application processes untrusted font files from web sources or user uploads. The vulnerability affects not only the FontForge application itself but also any software that relies on FontForge's font parsing capabilities or integrates with it for font manipulation tasks. This makes the impact particularly wide-ranging across the digital typography ecosystem where font processing is a common operation.
Mitigation strategies for this vulnerability should focus on immediate version updates to FontForge 20170731 or later, which contains the necessary patches to address the buffer over-read condition. Organizations should implement strict input validation controls when processing font files, particularly in environments where untrusted font content is handled. System administrators should consider implementing sandboxing mechanisms for font processing operations and establishing network segmentation to limit potential attack vectors. The vulnerability aligns with CWE-125, which specifically addresses out-of-bounds read conditions, and could potentially map to ATT&CK technique T1059.007 for script execution if exploitation leads to code execution. Regular security assessments of font processing applications and maintaining updated font libraries can help prevent exploitation attempts, while monitoring for unusual font processing patterns may help detect potential exploitation attempts in real-time environments.