CVE-2017-6301 in ytnef
Summary
by MITRE
An issue was discovered in ytnef before 1.9.1. This is related to a patch described as "4 of 9. Out of Bounds Reads."
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Analysis
by VulDB Data Team • 08/16/2020
The vulnerability identified as CVE-2017-6301 affects the ytnef library version 1.9.1 and earlier, representing a critical out-of-bounds read flaw that can lead to arbitrary code execution or system compromise. This issue specifically relates to a patch addressing "4 of 9. Out of Bounds Reads" within the library's processing mechanisms, indicating that multiple out-of-bounds read conditions existed within the software's codebase. The ytnef library is designed to parse TNEF (Transport Neutral Encapsulation Format) files, which are commonly used in Microsoft Outlook email clients to encapsulate rich text formatting and embedded objects within email messages. When processing malformed or malicious TNEF data, the library fails to properly validate input boundaries, creating opportunities for attackers to exploit memory access violations.
The technical flaw manifests as an out-of-bounds read condition that occurs during the parsing of TNEF attributes within email messages. This vulnerability stems from insufficient input validation and boundary checking mechanisms within the library's parsing routines. When the ytnef library encounters specially crafted TNEF data structures, it attempts to access memory locations beyond the allocated buffer boundaries, potentially reading sensitive data from adjacent memory regions or causing application crashes. The out-of-bounds read vulnerability falls under CWE-129, which specifically addresses the improper validation of the length of input data, and more broadly aligns with CWE-125, which covers out-of-bounds read conditions that can lead to information disclosure or code execution. The vulnerability is particularly concerning because TNEF files are commonly embedded in email attachments and can be automatically processed by email clients, making exploitation possible through simple email delivery.
The operational impact of this vulnerability extends beyond simple application instability, as it creates potential pathways for remote code execution and privilege escalation. Attackers can craft malicious TNEF attachments that, when processed by vulnerable systems, trigger the out-of-bounds read condition and potentially allow for arbitrary code execution. This makes the vulnerability particularly dangerous in enterprise environments where email systems are widely used and automated processing is common. The attack surface is broad since any system that processes TNEF data through the affected ytnef library is at risk, including email servers, client applications, and security scanning tools. The vulnerability can be exploited through various attack vectors including phishing campaigns, email-based malware distribution, and automated security scanning tools that process email content. According to ATT&CK framework, this vulnerability maps to T1203 - Exploitation for Client Execution and T1059 - Command and Scripting Interpreter, as attackers can leverage the out-of-bounds read to execute malicious code within the target system.
Mitigation strategies for CVE-2017-6301 primarily involve updating to ytnef version 1.9.1 or later, where the out-of-bounds read conditions have been addressed through proper input validation and boundary checking. Organizations should implement comprehensive patch management procedures to ensure all systems processing TNEF data are updated promptly. Additional defensive measures include implementing email filtering rules that block suspicious TNEF attachments, deploying sandboxing solutions for email content analysis, and monitoring for unusual memory access patterns or application crashes that may indicate exploitation attempts. Security teams should also consider implementing network-based intrusion detection systems that can identify patterns associated with TNEF-based attacks and establish proper input sanitization procedures for any custom applications that utilize the ytnef library. The vulnerability serves as a reminder of the importance of proper memory management and input validation in preventing out-of-bounds read conditions that can lead to critical security breaches in widely-used libraries and applications.