CVE-2014-9661 in FreeType
Summary
by MITRE
type42/t42parse.c in FreeType before 2.5.4 does not consider that scanning can be incomplete without triggering an error, which allows remote attackers to cause a denial of service (use-after-free) or possibly have unspecified other impact via a crafted Type42 font.
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Analysis
by VulDB Data Team • 03/08/2022
The vulnerability identified as CVE-2014-9661 affects the FreeType font rendering library version 2.5.3 and earlier, specifically within the type42/t42parse.c component responsible for parsing Type42 font formats. This flaw represents a critical security issue that demonstrates poor error handling practices in font parsing operations, creating potential pathways for remote exploitation. The vulnerability stems from the library's failure to properly validate scanning operations during Type42 font processing, where incomplete scanning operations do not necessarily result in error conditions as expected by the parser logic.
The technical implementation of this vulnerability occurs when FreeType encounters a malformed Type42 font file that triggers incomplete scanning behavior in the t42parse.c module. The parser does not adequately account for scenarios where scanning operations may terminate prematurely without generating appropriate error signals, leading to memory management inconsistencies. When the parsing process completes with incomplete data, the library continues processing potentially invalid memory references, creating conditions where freed memory locations may be accessed or reused, resulting in use-after-free conditions that can be exploited for denial of service attacks or potentially more severe consequences.
From an operational impact perspective, this vulnerability enables remote attackers to craft malicious Type42 font files that can trigger the flawed parsing logic when processed by vulnerable FreeType implementations. The exploitation potential extends beyond simple denial of service, as the use-after-free conditions could potentially be leveraged for arbitrary code execution depending on the specific system configuration and memory layout. The vulnerability affects any application or system that utilizes FreeType for font rendering, including web browsers, desktop applications, and operating system components that rely on this library for proper font handling.
The root cause of this vulnerability aligns with CWE-476, which addresses NULL pointer dereferences, and CWE-121, which covers stack-based buffer overflow conditions. The flaw demonstrates characteristics consistent with ATT&CK technique T1203, where adversaries manipulate application behavior through input manipulation to achieve unauthorized system access. Security researchers have noted that similar issues in font parsing libraries often represent high-value targets due to the widespread use of font rendering capabilities across different software platforms, making this vulnerability particularly dangerous in environments where users might encounter malicious font files through various attack vectors such as email attachments, web content, or file downloads.
Mitigation strategies for this vulnerability require immediate patching of FreeType libraries to version 2.5.4 or later, where the parsing logic has been corrected to properly handle incomplete scanning operations and ensure appropriate error conditions are triggered when scanning terminates without complete data processing. System administrators should also implement font validation measures and consider restricting font file types that can be processed by applications, particularly those that may be exposed to untrusted inputs. Additionally, monitoring for unusual memory access patterns and implementing proper memory management practices in applications that utilize FreeType can help detect and prevent exploitation attempts, while network segmentation and application whitelisting can limit potential attack surface exposure.