CVE-2007-2754 in Solaris
Summary
by MITRE
Integer signedness error in truetype/ttgload.c in Freetype 2.3.4 and earlier might allow remote attackers to execute arbitrary code via a crafted TTF image with a negative n_points value, which leads to an integer overflow and heap-based buffer overflow.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability described in CVE-2007-2754 represents a critical integer signedness error within the FreeType font rendering library version 2.3.4 and earlier. This flaw exists in the TrueType glyph loading component at line 1792 in the ttgload.c file, where the library processes font data without proper validation of the n_points parameter. The issue manifests when a maliciously crafted TrueType font file contains a negative value for the n_points field, which is intended to specify the number of points in a glyph outline. When this negative value is processed through the font loading pipeline, it creates an integer overflow condition that ultimately results in a heap-based buffer overflow.
The technical exploitation of this vulnerability occurs through a specific sequence of operations involving integer arithmetic and memory allocation. The FreeType library initializes a buffer using the n_points value directly without checking for negative inputs, causing the signed integer to be interpreted as an unsigned value during memory allocation calculations. This misinterpretation leads to a situation where the library allocates insufficient memory for the buffer, yet the subsequent processing attempts to write data beyond the allocated boundary. The CWE-190 classification applies here as this represents an integer overflow vulnerability, specifically involving the improper handling of signed integers in arithmetic operations. The flaw is categorized under CWE-129 as it involves an out-of-bounds write operation that occurs due to improper input validation.
The operational impact of this vulnerability extends beyond simple code execution, as it provides remote attackers with a pathway to achieve arbitrary code execution on systems that process untrusted font data. Systems utilizing FreeType for font rendering across various applications and operating systems become vulnerable, including web browsers, office suites, desktop environments, and any software that renders TrueType fonts. The attack vector requires a victim to view or process a specially crafted TTF file, which could be delivered through email attachments, web pages, or file sharing platforms. This vulnerability is particularly dangerous because it can be exploited silently without user interaction, and the attack can be performed remotely through web-based delivery mechanisms. The ATT&CK framework categorizes this under T1068 as a remote code execution attack through the exploitation of a software vulnerability in a widely used library, while T1203 represents the use of malicious files for initial access and privilege escalation.
Mitigation strategies for CVE-2007-2754 require immediate action to upgrade to FreeType version 2.3.5 or later, where the integer signedness error has been corrected through proper input validation and boundary checking. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing FreeType are updated promptly, particularly those running web browsers, document viewers, and desktop applications. Additional defensive measures include implementing strict file validation for font processing, deploying sandboxing mechanisms for font rendering operations, and configuring network security controls to block potentially malicious font files. The fix implemented in newer FreeType versions involves adding proper validation checks for the n_points parameter to ensure it remains within acceptable positive integer ranges before any memory allocation occurs. Security monitoring should include detection of unusual font processing patterns and memory allocation behaviors that might indicate exploitation attempts. System administrators should also consider implementing application whitelisting policies that restrict font file processing to trusted sources and applications. The vulnerability demonstrates the critical importance of input validation in cryptographic and font processing libraries, as these components often handle untrusted data from external sources and must maintain robust security boundaries to prevent exploitation.