CVE-2017-12141 in ytnef
Summary
by MITRE
In ytnef 1.9.2, a heap-based buffer overflow vulnerability was found in the function TNEFFillMapi in ytnef.c, which allows attackers to cause a denial of service via a crafted file.
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Analysis
by VulDB Data Team • 12/14/2022
The heap-based buffer overflow vulnerability identified as CVE-2017-12141 resides within the ytnef library version 1.9.2, specifically within the TNEFFillMapi function located in the ytnef.c source file. This vulnerability represents a critical security flaw that arises from improper bounds checking during the processing of TNEF (Transport Neutral Encapsulation Format) files, which are commonly used for encapsulating Microsoft Outlook messages and their attachments. The flaw occurs when the library attempts to parse maliciously crafted TNEF files that contain oversized data structures, leading to memory corruption in the heap allocation region.
The technical execution of this vulnerability involves the TNEFFillMapi function failing to validate the size of incoming data before attempting to copy it into pre-allocated heap buffers. When an attacker crafts a TNEF file containing oversized or malformed data fields, the function proceeds to copy this data without proper boundary checks, causing adjacent heap memory to be overwritten. This heap corruption can result in arbitrary code execution or complete application crash, depending on the memory layout and the specific nature of the overflow. The vulnerability falls under CWE-121 Heap-based Buffer Overflow, which is classified as a fundamental memory safety issue in software development practices.
The operational impact of CVE-2017-12141 extends beyond simple denial of service scenarios, as it can potentially enable remote code execution when the affected ytnef library is integrated into applications that process untrusted TNEF files. Systems that rely on ytnef for email processing, document handling, or file format conversion become vulnerable to exploitation by malicious actors who can craft specially designed TNEF attachments to trigger the buffer overflow. This vulnerability is particularly concerning in email servers, content filtering systems, and document processing applications that may encounter TNEF files from untrusted sources, as it provides a potential entry point for attackers to compromise these systems.
Mitigation strategies for CVE-2017-12141 should prioritize immediate patching of the ytnef library to version 1.9.3 or later, which contains the necessary fixes for the heap buffer overflow issue. Organizations should implement strict input validation procedures for all TNEF file processing, including size limitations and format verification before any parsing occurs. Network security measures such as email filtering and content inspection systems should be configured to scan for and block potentially malicious TNEF attachments. Additionally, the principle of least privilege should be applied when running applications that utilize ytnef, limiting the potential damage from successful exploitation. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving buffer overflow exploitation and privilege escalation, making it a significant concern for defensive security operations that must account for memory corruption vulnerabilities in third-party libraries.