CVE-2014-9656 in FreeType
Summary
by MITRE
The tt_sbit_decoder_load_image function in sfnt/ttsbit.c in FreeType before 2.5.4 does not properly check for an integer overflow, which allows remote attackers to cause a denial of service (out-of-bounds read) or possibly have unspecified other impact via a crafted OpenType font.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 03/08/2022
The vulnerability identified as CVE-2014-9656 represents a critical integer overflow flaw within the FreeType font rendering library, specifically within the tt_sbit_decoder_load_image function located in sfnt/ttsbit.c. This issue affects FreeType versions prior to 2.5.4 and demonstrates how improper input validation can lead to severe security consequences. The flaw occurs when processing OpenType fonts containing embedded bitmaps, where the function fails to adequately validate integer values during the bitmap decoding process, creating opportunities for malicious actors to manipulate font data and exploit the underlying system.
The technical implementation of this vulnerability stems from insufficient boundary checking during integer arithmetic operations within the bitmap loading routine. When FreeType processes a font with embedded bitmap data, the tt_sbit_decoder_load_image function calculates memory offsets and buffer sizes based on font metadata without proper overflow detection. This allows attackers to craft specially designed OpenType font files where the calculated buffer indices exceed valid memory boundaries, resulting in out-of-bounds read operations that can trigger system crashes or potentially enable further exploitation. The vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and demonstrates how such flaws can be leveraged for denial of service attacks.
The operational impact of CVE-2014-9656 extends beyond simple service disruption to potentially enable more sophisticated attack vectors. Remote attackers can leverage this vulnerability by delivering malicious font files through various attack vectors including web browsers, email attachments, or document viewers that utilize FreeType for font rendering. The out-of-bounds read conditions can cause applications to crash unpredictably, leading to denial of service across multiple platforms where FreeType is integrated, including web browsers, desktop applications, and server environments. Additionally, the unspecified other impacts mentioned in the vulnerability description suggest potential for information disclosure or code execution under certain conditions, particularly when combined with other vulnerabilities or in specific system configurations.
Mitigation strategies for this vulnerability require immediate patching of FreeType libraries to version 2.5.4 or later, which includes proper integer overflow checks and boundary validation. System administrators should prioritize updating all applications that depend on FreeType, including web browsers, office suites, and document processing software, to ensure comprehensive protection. Network defenders should implement content filtering measures to block suspicious font files and monitor for unusual font processing behavior. The remediation approach aligns with ATT&CK technique T1203, which involves the use of malicious files, and emphasizes the importance of maintaining up-to-date software libraries as a fundamental defense mechanism. Organizations should also consider implementing sandboxing techniques for font processing and establishing robust vulnerability management procedures to identify and remediate similar issues in third-party components.