CVE-2014-9747 in FreeType
Summary
by MITRE
The t42_parse_encoding function in type42/t42parse.c in FreeType before 2.5.4 does not properly update the current position for immediates-only mode, which allows remote attackers to cause a denial of service (infinite loop) via a Type42 font.
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Analysis
by VulDB Data Team • 08/23/2022
The vulnerability identified as CVE-2014-9747 resides within the FreeType font rendering library, specifically in the t42_parse_encoding function located in type42/t42parse.c. This flaw affects FreeType versions prior to 2.5.4 and represents a critical denial of service vulnerability that can be exploited remotely. The issue manifests when processing Type42 fonts, which are a specific font format used in PostScript and PDF document processing. FreeType is widely deployed across operating systems, web browsers, and applications that handle font rendering, making this vulnerability particularly dangerous as it can impact a broad range of software environments.
The technical root cause of this vulnerability stems from improper handling of position tracking within the Type42 font parsing logic. When the t42_parse_encoding function operates in immediates-only mode, it fails to correctly update the current position pointer as it processes font data. This position tracking mechanism is essential for maintaining proper parsing state and ensuring that the parser advances through the font file correctly. The failure to update the position pointer creates a scenario where the parser can become trapped in a loop, repeatedly processing the same data segment without making forward progress. This behavior constitutes a classic infinite loop vulnerability that consumes system resources and can effectively crash applications using the affected FreeType library.
The operational impact of CVE-2014-9747 extends beyond simple denial of service, as it can be leveraged in various attack scenarios. Remote attackers can craft malicious Type42 font files that, when processed by vulnerable applications, will trigger the infinite loop condition. This vulnerability affects web browsers, PDF viewers, desktop applications, and any software that relies on FreeType for font rendering. The attack surface is particularly broad since Type42 fonts can be embedded in various document formats, making it possible for attackers to exploit this vulnerability through email attachments, web content, or downloaded documents. The resource exhaustion caused by the infinite loop can lead to system instability, application crashes, and potentially allow for more sophisticated attacks if combined with other vulnerabilities.
Mitigation strategies for this vulnerability primarily focus on updating to FreeType version 2.5.4 or later, which contains the necessary patches to fix the position tracking issue. System administrators should prioritize patching affected applications and operating systems that depend on FreeType for font processing. Additional protective measures include implementing font validation mechanisms that can detect and reject malformed Type42 fonts before they are processed, as well as network-level filtering to prevent the delivery of potentially malicious font files. Organizations should also consider implementing application sandboxing and privilege separation to limit the impact if an attacker successfully exploits this vulnerability. From a cybersecurity perspective, this vulnerability aligns with CWE-835, which deals with infinite loops, and can be mapped to ATT&CK technique T1059.007 for the execution of malicious code through font processing. The vulnerability demonstrates the importance of proper state management in parsing routines and highlights how seemingly minor flaws in parsing logic can lead to significant security implications.