CVE-2021-21833 in ImageGear
Summary
by MITRE • 06/11/2021
An improper array index validation vulnerability exists in the TIF IP_planar_raster_unpack functionality of Accusoft ImageGear 19.9. A specially crafted malformed file can lead to an out-of-bounds write. An attacker can provide a malicious file to trigger this vulnerability.
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Analysis
by VulDB Data Team • 06/14/2021
The vulnerability identified as CVE-2021-21833 represents a critical improper array index validation flaw within the TIF IP_planar_raster_unpack functionality of Accusoft ImageGear version 19.9. This issue manifests as an out-of-bounds write condition that occurs when processing specially crafted malformed TIFF files. The vulnerability stems from insufficient validation of array indices during the unpacking process of planar raster data, creating a scenario where memory operations extend beyond allocated boundaries. The flaw is particularly concerning as it allows attackers to manipulate memory regions beyond the intended array limits, potentially leading to arbitrary code execution or system instability.
The technical implementation of this vulnerability involves the TIF IP_planar_raster_unpack function which handles the decompression and unpacking of planar raster data within TIFF image files. When processing malformed input files, the function fails to properly validate index values used for array access operations, allowing attackers to craft input data that causes array indices to reference memory locations outside the allocated array boundaries. This improper validation creates a predictable memory corruption scenario where the out-of-bounds write can overwrite adjacent memory regions, potentially corrupting critical data structures or executable code. The vulnerability is classified under CWE-129 as an "Improper Validation of Array Index" and represents a variant of buffer overflow conditions that can be exploited through crafted input files.
From an operational perspective, this vulnerability presents significant risks to systems that process TIFF image files using Accusoft ImageGear 19.9. Attackers can exploit this flaw by preparing malicious TIFF files that, when opened or processed by applications relying on this library, trigger the out-of-bounds write condition. The impact extends beyond simple system crashes to potentially enable remote code execution, particularly when the vulnerable library is used in web applications, document processing systems, or any environment where untrusted TIFF files might be processed. This vulnerability aligns with ATT&CK technique T1203 "Exploitation for Client Execution" and could be leveraged in broader attack chains targeting document processing workflows or web applications that handle image uploads.
Mitigation strategies for CVE-2021-21833 should prioritize immediate patching of Accusoft ImageGear to version 19.10 or later where the vulnerability has been addressed. Organizations should implement input validation controls that sanitize TIFF file inputs before processing, including implementing strict file format validation and boundary checking mechanisms. Network segmentation and application whitelisting can help reduce the attack surface by limiting which systems can process TIFF files. Additionally, deploying intrusion detection systems that monitor for suspicious file processing patterns and implementing regular security assessments of document handling workflows can provide early detection of exploitation attempts. The vulnerability demonstrates the importance of proper input validation in image processing libraries and highlights the need for comprehensive security testing of third-party components used in document processing applications.