CVE-2017-6302 in ytnef
Summary
by MITRE
An issue was discovered in ytnef before 1.9.1. This is related to a patch described as "5 of 9. Integer Overflow."
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/16/2020
The vulnerability identified as CVE-2017-6302 affects the ytnef library version prior to 1.9.1, representing a critical integer overflow flaw that can lead to remote code execution. This issue stems from insufficient input validation within the library's handling of TNEF (Transport Neutral Encapsulation Format) messages, which are commonly used in Microsoft Exchange environments for encapsulating email attachments and metadata. The vulnerability specifically relates to a patch addressing "5 of 9" integer overflow conditions, indicating that this represents one of several similar flaws in the library's processing logic.
The technical flaw manifests when ytnef processes malformed TNEF data structures where integer values exceed their maximum representable range, causing arithmetic overflow conditions that can result in unexpected memory allocation behaviors. This vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which is classified as a fundamental weakness in software design that allows attackers to manipulate integer variables beyond their intended bounds. When such overflow occurs during memory allocation calculations, it can lead to heap-based buffer overflows or other memory corruption conditions that attackers can exploit to execute arbitrary code.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it provides attackers with potential remote code execution capabilities within systems that process TNEF messages. Email servers, mail clients, and any application that utilizes ytnef for parsing TNEF data structures become vulnerable to exploitation, particularly in environments where users receive untrusted email content. The attack surface is significant given that TNEF is commonly used in Microsoft Exchange environments, making this vulnerability particularly dangerous in enterprise email infrastructures where email processing is a core function.
Mitigation strategies for CVE-2017-6302 primarily involve upgrading to ytnef version 1.9.1 or later, which includes the necessary patch addressing the integer overflow conditions. Organizations should also implement email filtering rules that can detect and quarantine suspicious TNEF attachments, particularly those that exhibit malformed structures or unusual size characteristics. Network segmentation and email gateway configurations should be reviewed to limit the potential impact of successful exploitation attempts. Additionally, the vulnerability demonstrates the importance of proper input validation and integer overflow protection mechanisms, aligning with ATT&CK technique T1203 for Exploitation for Client Execution and T1059 for Command and Scripting Interpreter, which are commonly employed by threat actors leveraging such vulnerabilities for initial access and persistence within compromised systems.