CVE-2017-9403 in LibTIFF
Summary
by MITRE
In LibTIFF 4.0.7, a memory leak vulnerability was found in the function TIFFReadDirEntryLong8Array in tif_dirread.c, which allows attackers to cause a denial of service via a crafted file.
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Analysis
by VulDB Data Team • 10/13/2019
The memory leak vulnerability identified as CVE-2017-9403 resides within the LibTIFF library version 4.0.7, specifically within the TIFFReadDirEntryLong8Array function located in the tif_dirread.c source file. This flaw represents a classic resource management issue that can be exploited to consume excessive system memory through carefully crafted TIFF image files. The vulnerability manifests when the library processes directory entries containing 64-bit integer arrays, creating a scenario where allocated memory is not properly released during the parsing process. Such memory leaks can accumulate over time and eventually lead to system instability or complete resource exhaustion, making this a significant concern for applications that process untrusted TIFF files.
The technical implementation of this vulnerability stems from improper memory deallocation within the TIFFReadDirEntryLong8Array function, which is responsible for reading directory entries containing 64-bit integer values. When processing malformed TIFF files, the function fails to properly clean up allocated memory blocks, resulting in memory fragmentation and gradual consumption of available system resources. This type of vulnerability falls under CWE-401, which specifically addresses memory leaks in software systems. The flaw is particularly dangerous because it can be triggered through normal file parsing operations, requiring no special privileges or complex exploitation techniques beyond crafting a malicious TIFF file.
From an operational standpoint, this vulnerability creates substantial risk for systems that handle TIFF image processing, including web applications, image servers, and document management systems. Attackers can leverage this weakness to perform denial of service attacks by uploading or transmitting specially crafted TIFF files that cause the target system to consume increasing amounts of memory until the service becomes unavailable or crashes. The impact extends beyond simple resource exhaustion, as it can affect system availability for legitimate users and potentially disrupt critical business operations. Systems running vulnerable versions of LibTIFF are particularly at risk when processing user-uploaded content or when serving images from untrusted sources, making this vulnerability a prime target for exploitation in web-based attack scenarios.
Mitigation strategies for CVE-2017-9403 should prioritize immediate patching of affected LibTIFF installations to version 4.0.8 or later, which contains the necessary memory management fixes. Organizations should implement comprehensive input validation and sanitization measures for all TIFF file processing, including file format verification and size limits to prevent excessive memory consumption. Network-level protections such as file type filtering and sandboxing mechanisms can provide additional defense layers against exploitation attempts. Security monitoring should include detection of unusual memory usage patterns and resource consumption spikes that may indicate exploitation attempts. The vulnerability also highlights the importance of regular security audits and dependency management practices to identify and remediate similar issues before they can be exploited in production environments. This case exemplifies the critical nature of proper memory management in security-critical libraries and demonstrates how seemingly minor implementation flaws can result in significant operational impacts and service disruption.