CVE-2017-9474 in ytnef
Summary
by MITRE
In ytnef 1.9.2, the DecompressRTF 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-2017-9474 represents a critical heap-based buffer over-read flaw within the ytnef library version 1.9.2. This issue specifically affects the DecompressRTF function located in the lib/ytnef.c source file, creating a significant security risk for applications that rely on this library for processing TNEF (Transport Neutral Encapsulation Format) files. The vulnerability arises from inadequate input validation and memory management practices during the decompression process of RTF content within TNEF attachments.
The technical exploitation of this vulnerability occurs when a maliciously crafted TNEF file is processed by software utilizing ytnef library version 1.9.2. During the DecompressRTF function execution, the application fails to properly validate the bounds of memory allocations, leading to a heap-based buffer over-read condition. This condition allows attackers to manipulate memory access patterns in a way that causes the application to read beyond allocated memory boundaries, resulting in unpredictable behavior and ultimately leading to application crashes or complete system instability. The vulnerability is classified as a heap-based buffer over-read according to CWE-125, which specifically addresses out-of-bounds read conditions in heap memory allocations.
From an operational impact perspective, this vulnerability creates a reliable denial of service condition that can be exploited by remote attackers without requiring any special privileges or authentication. The flaw affects any application that integrates ytnef library functionality for processing email attachments, particularly those handling TNEF formatted content such as Microsoft Outlook messages. The crash condition can be triggered through simple file processing operations, making it highly exploitable in automated attack scenarios. This vulnerability directly maps to the ATT&CK technique T1499.004 for Network Denial of Service, as it enables remote adversaries to disrupt services through application instability.
The remediation approach for CVE-2017-9474 requires immediate upgrading to ytnef library version 1.9.3 or later, where the buffer over-read issue has been addressed through proper bounds checking and memory validation. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing ytnef functionality receive the security update promptly. Additionally, input validation measures should be enhanced at the application level to provide additional defense-in-depth protection. Security monitoring should be implemented to detect potential exploitation attempts, and network segmentation can help limit the impact of successful attacks. The fix typically involves implementing proper bounds checking mechanisms and ensuring that memory allocations are validated before any read operations occur, preventing the heap-based buffer over-read condition that leads to application crashes and denial of service conditions.