CVE-2017-7448 in Dropbox Lepton
Summary
by MITRE
The allocate_channel_framebuffer function in uncompressed_components.hh in Dropbox Lepton 1.2.1 allows remote attackers to cause a denial of service (divide-by-zero error and application crash) via a malformed JPEG image.
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Analysis
by VulDB Data Team • 11/27/2022
The vulnerability identified as CVE-2017-7448 resides within the Dropbox Lepton 1.2.1 image processing library, specifically in the allocate_channel_framebuffer function located in the uncompressed_components.hh file. This flaw represents a classic divide-by-zero error that occurs when processing malformed JPEG images, creating a critical security weakness in the image decompression pipeline. The issue stems from insufficient input validation and error handling mechanisms within the image processing component, which fails to properly validate image dimensions before attempting mathematical operations that could result in division by zero conditions.
The technical exploitation of this vulnerability occurs when a remote attacker crafts a specially malformed JPEG image that contains invalid dimension parameters. When the Dropbox Lepton library attempts to process such an image through the allocate_channel_framebuffer function, it encounters a scenario where the frame buffer allocation calculation involves a division operation with a zero denominator. This mathematical error triggers an immediate application crash, effectively causing a denial of service condition that renders the affected system or application unavailable to legitimate users. The vulnerability operates at the level of image decompression and memory allocation, making it particularly dangerous as it can be triggered simply by attempting to open or process the malicious image file.
From an operational impact perspective, this vulnerability creates significant risks for systems that rely on Dropbox Lepton for image processing tasks, particularly those handling user-uploaded content or processing external image files. The denial of service condition can be easily exploited by attackers to disrupt services, potentially leading to complete application unavailability or system instability. This vulnerability directly impacts the availability aspect of the CIA triad and can be leveraged in broader attack scenarios where service disruption is the primary objective. The flaw affects systems that process JPEG images through the Lepton library, which could include web applications, content management systems, or any software that incorporates this image processing component.
The vulnerability aligns with CWE-369, which specifically addresses the divide by zero weakness, and demonstrates how inadequate input validation can lead to critical system failures. From an ATT&CK framework perspective, this vulnerability maps to the privilege escalation and denial of service tactics, as it allows remote attackers to disrupt system availability without requiring elevated privileges. The attack surface is broad since any application using Dropbox Lepton for JPEG image processing is potentially vulnerable, including web applications, mobile apps, and server-side image processing systems. Organizations should implement immediate mitigations including updating to patched versions of the Dropbox Lepton library, implementing input validation for image files, and deploying network-level controls to prevent malicious image uploads. Additionally, the vulnerability underscores the importance of proper error handling in image processing libraries and highlights the need for robust sanitization of image metadata before processing to prevent similar mathematical errors from occurring in critical system components.