CVE-2017-12944 in LibTIFF
Summary
by MITRE
The TIFFReadDirEntryArray function in tif_read.c in LibTIFF 4.0.8 mishandles memory allocation for short files, which allows remote attackers to cause a denial of service (allocation failure and application crash) in the TIFFFetchStripThing function in tif_dirread.c during a tiff2pdf invocation.
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Analysis
by VulDB Data Team • 01/09/2021
The vulnerability identified as CVE-2017-12944 resides within the LibTIFF library version 4.0.8, specifically within the TIFFReadDirEntryArray function located in the tif_read.c source file. This flaw represents a classic memory management issue that occurs when processing malformed or truncated TIFF files, creating a scenario where the library fails to properly handle insufficient data during the parsing process. The vulnerability manifests when the library encounters short or incomplete TIFF files that do not contain the expected data structures, leading to improper memory allocation decisions that can ultimately result in application instability.
The technical flaw stems from the improper handling of memory allocation within the TIFFReadDirEntryArray function, which is responsible for reading directory entries from TIFF files. When processing malformed input files, the function fails to validate the length of data available before attempting memory allocation operations. This particular issue becomes exploitable during the TIFFFetchStripThing function execution in tif_dirread.c when a tiff2pdf conversion process is initiated. The flaw creates a condition where insufficient data triggers an allocation failure that causes the application to crash, effectively enabling a denial of service attack against systems processing TIFF files through the affected library.
From an operational impact perspective, this vulnerability creates significant risks for systems that process TIFF images, particularly those that accept user-uploaded content or process external image files. The denial of service condition can be easily triggered by sending a specially crafted short TIFF file to any application that utilizes LibTIFF 4.0.8 for image processing, including document conversion tools, image viewers, and content management systems. The vulnerability aligns with CWE-129, which addresses improper validation of array indices, and more specifically with CWE-704, concerning improper handling of memory allocation failures. This makes the vulnerability particularly dangerous in environments where automated processing occurs, as attackers can systematically disrupt services by submitting malicious files that trigger the memory allocation failure.
The exploitation of this vulnerability follows patterns consistent with the attack techniques described in the MITRE ATT&CK framework under the T1499 category, which covers network denial of service attacks. The attack vector requires remote delivery of a malformed TIFF file that can be processed by any application utilizing the vulnerable LibTIFF library, making it a widespread concern across various software ecosystems that depend on TIFF image processing capabilities. Organizations using the affected library should prioritize patching their systems and implementing input validation measures to prevent the processing of untrusted TIFF files until the vulnerability is addressed through proper software updates.
This vulnerability demonstrates the critical importance of proper memory management and input validation in image processing libraries, where malformed input can lead to catastrophic failures. The flaw serves as a reminder of how seemingly minor issues in low-level library functions can create significant security risks when deployed in production environments. The proper mitigation involves updating to LibTIFF versions that contain the patched TIFFReadDirEntryArray function and implementing additional safeguards such as file size limits, content type validation, and proper error handling in applications that process TIFF files. Organizations should also consider implementing sandboxing techniques for image processing tasks to contain potential impacts from similar vulnerabilities that may be discovered in the future.