CVE-2014-9745 in FreeType
Summary
by MITRE
The parse_encoding function in type1/t1load.c in FreeType before 2.5.3 allows remote attackers to cause a denial of service (infinite loop) via a "broken number-with-base" in a Postscript stream, as demonstrated by 8#garbage.
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Analysis
by VulDB Data Team • 06/15/2022
The vulnerability identified as CVE-2014-9745 represents a critical denial of service flaw within the FreeType font rendering library, specifically affecting versions prior to 2.5.3. This issue resides in the parse_encoding function located within the type1/t1load.c source file, which is responsible for processing Type 1 font files that utilize PostScript encoding. The flaw manifests when the library encounters malformed PostScript streams containing what are termed "broken number-with-base" constructs, particularly exemplified by the pattern 8#garbage. Such malformed input sequences can trigger an infinite loop within the parsing logic, causing the affected application to consume excessive CPU resources and potentially become unresponsive.
The technical exploitation of this vulnerability occurs through the manipulation of PostScript font data where the parser encounters a number specified with an explicit base prefix followed by invalid characters. In PostScript syntax, numbers can be expressed using different bases such as 8# for octal, 16# for hexadecimal, or 2# for binary formats. When the parser encounters 8#garbage, it attempts to process the octal number but fails to properly handle the subsequent garbage characters, leading to a control flow issue that results in an infinite loop. This behavior represents a classic example of inadequate input validation and error handling within cryptographic and font processing libraries, as defined by CWE-691. The vulnerability demonstrates how malformed data processing can lead to resource exhaustion and system instability, particularly in applications that rely on FreeType for font rendering operations.
The operational impact of CVE-2014-9745 extends beyond simple service disruption, as it can be leveraged by remote attackers to perform denial of service attacks against systems running vulnerable FreeType implementations. Applications that process untrusted font files, including web browsers, document viewers, and graphic design software, become susceptible to this attack vector. The infinite loop condition can cause applications to hang indefinitely or consume excessive computational resources, effectively rendering the target system or application unavailable to legitimate users. This vulnerability aligns with ATT&CK technique T1499.004, which describes the use of resource exhaustion attacks to deny service to legitimate users. The impact is particularly severe in server environments where multiple concurrent requests could be simultaneously affected, leading to cascading failures and system-wide degradation.
Mitigation strategies for CVE-2014-9745 primarily focus on updating to FreeType version 2.5.3 or later, which includes patched implementations that properly handle malformed PostScript number formats. System administrators should prioritize patching affected applications that utilize FreeType, particularly those handling untrusted font data from web sources or user uploads. Additional defensive measures include implementing input validation and sanitization for font files, deploying intrusion detection systems that can identify anomalous parsing behavior, and configuring applications to limit processing time for font rendering operations. Organizations should also consider implementing sandboxing mechanisms for font processing to contain potential impacts, and regularly audit their software dependencies to ensure all components are up to date with security patches. The vulnerability serves as a reminder of the importance of robust input validation in cryptographic libraries and font processing systems, as these components often form critical parts of application security and user experience.