CVE-2017-17942 in LibTIFF
Summary
by MITRE
In LibTIFF 4.0.9, there is a heap-based buffer over-read in the function PackBitsEncode in tif_packbits.c.
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Analysis
by VulDB Data Team • 12/18/2019
The vulnerability identified as CVE-2017-17942 represents a critical heap-based buffer over-read flaw within the LibTIFF library version 4.0.9. This issue specifically manifests in the PackBitsEncode function located within the tif_packbits.c source file, making it a significant concern for systems that process TIFF image files. The vulnerability stems from inadequate bounds checking during the encoding process of TIFF files using the PackBits compression algorithm, which is commonly employed in scientific imaging, medical imaging, and other applications requiring lossless image compression.
The technical flaw occurs when the PackBitsEncode function processes certain malformed or specially crafted TIFF input data that triggers an improper memory access pattern. During the encoding operation, the function attempts to read beyond the allocated heap memory boundaries, potentially accessing uninitialized or already freed memory locations. This over-read condition can result in information disclosure, application crashes, or in some scenarios, arbitrary code execution depending on the specific memory layout and exploitation conditions. The vulnerability is classified under CWE-125 as an out-of-bounds read, which represents a fundamental memory safety issue that can be exploited by attackers to gain unauthorized access to system resources or disrupt normal application functionality.
From an operational impact perspective, this vulnerability affects any software system that relies on LibTIFF 4.0.9 for TIFF file processing, including but not limited to image viewers, document management systems, medical imaging equipment, scientific data analysis platforms, and web applications that handle TIFF uploads. The attack surface is particularly broad since TIFF format is widely used across multiple industries and applications. When exploited, the buffer over-read can cause denial of service conditions through application crashes or more severe impacts if the attacker can leverage the information disclosure aspect to gain insights into memory layouts for further exploitation. The vulnerability is particularly concerning in server environments where TIFF files are processed without proper input validation, as it can be triggered by simply uploading a malicious TIFF file.
Mitigation strategies for CVE-2017-17942 should prioritize immediate patching of the LibTIFF library to version 4.0.10 or later, which contains the necessary fixes for the buffer over-read issue. Organizations should conduct comprehensive vulnerability assessments to identify all systems and applications that utilize the affected library version, particularly those handling user-uploaded TIFF files or processing external TIFF data sources. Input validation and sanitization measures should be implemented at multiple layers, including file format validation, size restrictions, and content analysis before any processing occurs. Additionally, system administrators should consider implementing network segmentation, access controls, and monitoring solutions to detect potential exploitation attempts. The remediation process should align with industry best practices and security frameworks such as those recommended by the ATT&CK framework, particularly focusing on defenses against code injection and memory corruption attacks. Regular security updates and patch management procedures should be strengthened to prevent similar vulnerabilities from being introduced in future versions of the library or related software components.