CVE-2017-9472 in ytnef
Summary
by MITRE
In ytnef 1.9.2, the SwapDWord function in lib/ytnef.c allows remote attackers to cause a denial of service (heap-based buffer over-read and application crash) via a crafted file.
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Analysis
by VulDB Data Team • 12/08/2022
The vulnerability identified as CVE-2017-9472 resides within the ytnef library version 1.9.2, specifically within the SwapDWord function located in the lib/ytnef.c source file. This issue represents a heap-based buffer over-read condition that can be exploited by remote attackers to execute a denial of service attack against affected systems. The ytnef library is commonly used for parsing TNEF (Transport Neutral Encapsulation Format) files, which are frequently encountered in email attachments and other communication protocols. When processing maliciously crafted TNEF files, the SwapDWord function fails to properly validate buffer boundaries, leading to memory access violations that result in application crashes and service disruption.
The technical flaw manifests through improper input validation within the SwapDWord function where the library attempts to manipulate byte order in 32-bit integers without adequate boundary checks. This function processes data that may contain malformed or crafted values, causing the program to read beyond allocated memory boundaries in the heap. The vulnerability stems from a lack of proper bounds checking mechanisms that should validate the size and content of data before processing. According to CWE classification, this vulnerability maps to CWE-125: Out-of-bounds Read, which is a common weakness in software systems where programs access memory locations outside the intended buffer boundaries. The issue is particularly concerning as it can be triggered remotely through the processing of maliciously formatted TNEF files, making it a significant security concern for systems that handle email attachments or other TNEF-based data.
The operational impact of CVE-2017-9472 extends beyond simple application crashes, as it can effectively render systems unavailable to legitimate users through sustained denial of service conditions. When exploited, the vulnerability can cause applications utilizing the ytnef library to terminate unexpectedly, requiring system administrators to restart services and potentially disrupting business operations. This type of vulnerability is particularly dangerous in email servers, collaboration platforms, and other systems that automatically process TNEF attachments. From an ATT&CK framework perspective, this vulnerability aligns with the technique T1499.004: Endpoint Denial of Service, where adversaries can disrupt services by causing application crashes or system instability. The remote exploitability of this vulnerability means that attackers can trigger the condition without requiring physical access to the target system, making it a particularly attractive vector for attackers seeking to disrupt services.
Mitigation strategies for CVE-2017-9472 should focus on immediate remediation through library updates and implementation of input validation measures. The most effective solution involves upgrading to a patched version of the ytnef library where the SwapDWord function has been corrected to include proper buffer boundary checks and input validation. System administrators should also implement defensive measures such as sandboxing TNEF file processing, implementing strict file format validation, and deploying intrusion detection systems that can identify suspicious file processing patterns. Additionally, organizations should consider implementing network segmentation and access controls to limit exposure to potentially malicious TNEF files. The vulnerability highlights the importance of proper memory management practices and the need for comprehensive testing of input validation mechanisms, particularly in libraries that handle untrusted data from external sources. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other components of the system that may be vulnerable to similar buffer over-read conditions.