CVE-2014-9663 in FreeType
Summary
by MITRE
The tt_cmap4_validate function in sfnt/ttcmap.c in FreeType before 2.5.4 validates a certain length field before that field s value is completely calculated, which allows remote attackers to cause a denial of service (out-of-bounds read) or possibly have unspecified other impact via a crafted cmap SFNT table.
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Analysis
by VulDB Data Team • 04/16/2022
The vulnerability identified as CVE-2014-9663 represents a critical buffer over-read flaw within the FreeType font rendering library, specifically within the tt_cmap4_validate function located in sfnt/ttcmap.c. This issue affects FreeType versions prior to 2.5.4 and demonstrates a classic software security weakness where validation occurs before data processing is complete, creating a window for exploitation. The vulnerability resides in the cmap SFNT table processing logic where the system attempts to validate a length field before the actual value of that field has been fully computed, leading to unpredictable behavior and potential system compromise.
The technical implementation of this flaw stems from improper order of operations within the font validation routine. When processing cmap tables, FreeType first validates a length field without ensuring that the field's value has been completely calculated or sanitized. This premature validation allows attackers to craft malicious font files containing specially crafted cmap data that can trigger an out-of-bounds memory read condition. The flaw operates at the intersection of font parsing and memory safety, where the validation logic is executed before the data processing phase is complete, creating a scenario where invalid memory access can occur during the validation process itself.
From an operational impact perspective, this vulnerability enables remote attackers to execute denial of service attacks against systems running affected FreeType versions. The out-of-bounds read condition can cause application crashes or system instability, effectively rendering font rendering services unavailable to legitimate users. Additionally, the unspecified other impacts suggest potential for more severe consequences including information disclosure or execution of arbitrary code, particularly when the vulnerable library is used in web browsers, email clients, or other applications that process untrusted font data. The vulnerability affects a wide range of applications that depend on FreeType for font rendering, making it particularly dangerous in enterprise environments where font processing occurs frequently.
The mitigation strategy for CVE-2014-9663 involves immediate upgrade to FreeType version 2.5.4 or later, which contains the necessary patch to fix the validation order issue. Organizations should also implement comprehensive font validation policies that include sandboxing font processing operations, using automated tools to scan font files for malicious content, and deploying network-based intrusion detection systems that can identify suspicious font-related traffic patterns. This vulnerability aligns with CWE-129, which addresses improper validation of array indices, and maps to ATT&CK technique T1059.007 for application layer execution, as the flaw enables remote code execution through crafted font files. System administrators should also consider implementing least privilege principles for font processing services and regularly audit font handling components within their applications to prevent similar vulnerabilities from emerging in the future.