CVE-2012-5669 in FreeType
Summary
by MITRE
The _bdf_parse_glyphs function in FreeType before 2.4.11 allows context-dependent attackers to cause a denial of service (crash) and possibly execute arbitrary code via vectors related to BDF fonts and an incorrect calculation that triggers an out-of-bounds read.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 04/20/2021
The vulnerability identified as CVE-2012-5669 resides within the FreeType font rendering library, specifically in the _bdf_parse_glyphs function that processes Bitmap Distribution Format fonts. This flaw represents a critical security issue affecting FreeType versions prior to 2.4.11, where the library fails to properly validate input data when parsing BDF font files. The vulnerability manifests as a context-dependent flaw that can be exploited by attackers who craft malicious BDF font files designed to trigger the problematic code path. The root cause lies in an incorrect calculation within the parsing logic that leads to an out-of-bounds memory read condition, which can result in unpredictable behavior ranging from application crashes to potential code execution. This vulnerability is particularly concerning because FreeType serves as a fundamental component in numerous operating systems, applications, and web browsers that rely on proper font rendering capabilities, making it a prime target for exploitation in various attack scenarios.
The technical implementation of this vulnerability stems from improper bounds checking within the BDF font parsing routine where the _bdf_parse_glyphs function fails to validate the size and structure of glyph data before attempting to access memory locations. When processing maliciously crafted BDF font files, the function performs calculations that assume certain data structures conform to expected formats, but when these assumptions are violated through crafted input, the calculation results in memory addresses that extend beyond the allocated buffer boundaries. This out-of-bounds read condition can cause the application to crash due to memory access violations, or more severely, if the attacker can control the memory contents accessed, potentially execute arbitrary code within the context of the vulnerable application. The vulnerability's context-dependence means that exploitation requires specific conditions related to how the font data is processed and rendered, but once triggered, the impact can be significant given FreeType's widespread use across different software platforms and operating systems.
The operational impact of CVE-2012-5669 extends far beyond simple denial of service scenarios, as it represents a potential vector for remote code execution in applications that utilize FreeType for font rendering. Systems that process untrusted font data, such as web browsers, document viewers, and graphic applications, become vulnerable to attacks that could lead to complete system compromise. The vulnerability affects not only desktop operating systems but also mobile platforms and embedded systems that rely on FreeType for their graphical user interfaces. Security researchers have classified this issue as having high severity due to its potential for arbitrary code execution, and it aligns with CWE-129, which describes improper validation of array indices, and CWE-125, which covers out-of-bounds read conditions. The attack surface is broad since FreeType is integrated into numerous software stacks including the Linux kernel, various web browsers, office suites, and graphic design applications, making exploitation possible through multiple attack vectors including email attachments, web content, and file downloads.
Mitigation strategies for CVE-2012-5669 primarily focus on upgrading to FreeType version 2.4.11 or later, which contains the necessary patches to address the out-of-bounds read vulnerability. System administrators should prioritize updating FreeType across all affected systems, particularly those that process untrusted font data or serve as font rendering engines for web browsers and document viewers. Additional protective measures include implementing strict input validation for font files, deploying sandboxing techniques for font processing, and configuring applications to use safer parsing routines that include proper bounds checking. The vulnerability demonstrates the importance of proper input validation and memory management in font rendering libraries, and aligns with ATT&CK technique T1068, which covers exploit for privilege escalation, as the potential for code execution makes this a significant threat. Organizations should also consider implementing network segmentation and monitoring for suspicious font-related file transfers, as well as establishing incident response procedures specifically addressing font-based vulnerabilities. Regular security assessments and vulnerability scanning should include checks for outdated FreeType installations to prevent exploitation of this and similar legacy vulnerabilities.