CVE-2017-5867 in ownCloud Server
Summary
by MITRE
ownCloud Server before 8.1.11, 8.2.x before 8.2.9, 9.0.x before 9.0.7, and 9.1.x before 9.1.3 allows remote authenticated users to cause a denial of service (server hang and logfile flooding) via a one bit BMP file.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 09/04/2020
The vulnerability identified as CVE-2017-5867 represents a significant denial of service weakness within ownCloud Server implementations across multiple version branches. This flaw specifically affects servers running versions prior to the mentioned patches, creating a scenario where authenticated remote attackers can exploit a seemingly benign one-bit BMP file to disrupt server operations. The vulnerability manifests through the processing of specially crafted bitmap image files that trigger abnormal server behavior, resulting in system resource exhaustion and operational disruption.
The technical root cause of this vulnerability lies in the insufficient input validation and error handling mechanisms within the ownCloud server's image processing pipeline. When a one-bit BMP file is uploaded or processed, the server's handling routine fails to properly validate the file structure and content, leading to an infinite loop or excessive resource consumption during the decoding process. This flaw operates at the intersection of image format parsing and memory management, where the server's inability to gracefully handle malformed image data causes it to become unresponsive. The vulnerability is categorized under CWE-248, which addresses the exposure of an exception to an untrusted environment, and specifically relates to improper input validation in image file processing. The ATT&CK framework classification places this under T1499.004, which covers network denial of service attacks through resource exhaustion.
The operational impact of CVE-2017-5867 extends beyond simple service interruption to create substantial administrative overhead and system instability. Server administrators face the challenge of dealing with flooded logfiles that contain repetitive error messages generated by the malformed file processing attempts, making system monitoring and troubleshooting significantly more difficult. The server hangs occur because the processing routine becomes trapped in loops or consumes excessive CPU cycles, effectively rendering the service unavailable to legitimate users. This vulnerability particularly impacts organizations relying on ownCloud for file sharing and collaboration, as it can be exploited by malicious users with valid credentials to disrupt business operations and potentially cause cascading failures in dependent systems.
Mitigation strategies for this vulnerability require immediate implementation of the vendor-provided patches for all affected version branches, specifically updating to ownCloud Server 8.1.11, 8.2.9, 9.0.7, and 9.1.3. Organizations should implement additional defensive measures including network-level filtering to restrict image file uploads, implementing strict file type validation, and configuring resource limits on file processing services. System administrators should also establish monitoring protocols to detect unusual resource consumption patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of robust input validation and proper error handling in file processing systems, emphasizing the need for comprehensive security testing of file format parsers and image handling components within enterprise file sharing platforms.