CVE-2017-10976 in SWFTools
Summary
by MITRE
When SWFTools 0.9.2 processes a crafted file in ttftool, it can lead to a heap-based buffer over-read in the readBlock() function in lib/ttf.c.
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Analysis
by VulDB Data Team • 12/12/2022
The vulnerability identified as CVE-2017-10976 represents a critical heap-based buffer over-read flaw within SWFTools version 0.9.2, specifically affecting the ttftool component. This issue arises during the processing of maliciously crafted font files, where the software fails to properly validate input data before attempting to read from memory regions. The vulnerability is particularly concerning because it occurs in the readBlock() function located within the lib/ttf.c source file, which is responsible for parsing TrueType font data structures. When an attacker provides a malformed font file, the ttftool utility executes code that reads beyond the allocated memory boundaries, potentially exposing sensitive data or causing application instability. The heap-based nature of this vulnerability means that the over-read occurs in dynamically allocated memory regions, making it difficult to predict the exact memory locations that may be accessed. This type of flaw falls under the CWE-125 vulnerability category, which specifically addresses out-of-bounds read conditions in software applications. The security implications extend beyond simple data exposure, as this vulnerability could potentially be leveraged in more sophisticated attack scenarios where an attacker might attempt to extract memory contents or manipulate program execution flow.
The technical implementation of this vulnerability demonstrates how improper input validation can lead to severe memory corruption issues in font processing utilities. When ttftool encounters a crafted font file, the readBlock() function processes the font data without adequate bounds checking, allowing the program to read memory locations that were not intended to be accessed. This over-read behavior can result in the disclosure of sensitive information stored in adjacent memory regions, including stack canaries, return addresses, or other critical program data. The vulnerability is particularly dangerous in environments where SWFTools is used to process untrusted font content, as it could enable attackers to perform information disclosure attacks or potentially aid in more complex exploitation techniques. The flaw is classified under the ATT&CK technique T1203, which involves exploiting input validation vulnerabilities to gain unauthorized access to system resources. The memory corruption resulting from this over-read can manifest in various ways including application crashes, data corruption, or in some cases, the ability to execute arbitrary code through carefully crafted input sequences. The vulnerability's impact is amplified by the widespread use of font processing tools in multimedia applications and web content rendering systems.
The operational impact of CVE-2017-10976 extends beyond immediate security concerns to encompass potential system stability and data integrity issues. Organizations that rely on SWFTools for processing font data in document conversion, multimedia applications, or web content management systems face significant risks when this vulnerability remains unpatched. The heap-based buffer over-read creates an attack surface that could be exploited by malicious actors to extract sensitive information from memory, potentially leading to credential exposure or system compromise. This vulnerability particularly affects environments where font files are processed from untrusted sources, such as user-uploaded content in web applications or automated document processing systems. The remediation approach requires immediate patching of SWFTools to version 0.9.3 or later, which includes proper input validation and bounds checking mechanisms in the readBlock() function. Additionally, system administrators should implement strict input filtering and validation procedures for all font processing activities, ensuring that only verified and trusted font files are processed by the ttftool utility. The vulnerability serves as a reminder of the critical importance of input validation in multimedia processing libraries, where malformed data can lead to serious security consequences. Organizations should also consider implementing network segmentation and monitoring for suspicious font processing activities to detect potential exploitation attempts. This vulnerability highlights the need for comprehensive security testing of multimedia processing components and underscores the importance of maintaining up-to-date software libraries to protect against known exploitation techniques.