CVE-2017-5188 in Open Build Service
Summary
by MITRE
The bs_worker code in open build service before 20170320 followed relative symlinks, allowing reading of files outside of the package source directory during build, allowing leakage of private information.
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Analysis
by VulDB Data Team • 02/16/2023
The vulnerability identified as CVE-2017-5188 resides within the bs_worker component of the Open Build Service platform, a distributed build system designed to automate software package compilation across multiple architectures and distributions. This issue affects versions of the Open Build Service released prior to March 20, 2017, creating a significant security risk through improper handling of symbolic links during the package building process. The flaw stems from the system's failure to properly validate or restrict symbolic link resolution, allowing malicious actors to exploit this weakness for unauthorized data access.
The technical implementation of this vulnerability involves the bs_worker process which handles package building operations and maintains a specific working directory structure for source code and build artifacts. During the build process, the system creates symbolic links to reference various source files and dependencies, but due to insufficient validation of these links, the system follows relative symbolic links without proper restrictions. This behavior enables attackers to craft malicious package structures containing carefully positioned symbolic links that point outside the designated package source directory, effectively bypassing the intended security boundaries that isolate build processes from the broader filesystem.
The operational impact of CVE-2017-5188 represents a critical information disclosure vulnerability that can result in unauthorized access to sensitive data stored on the build server. Attackers exploiting this vulnerability can potentially read files from arbitrary locations on the filesystem, including configuration files, private keys, source code repositories, and other confidential information that should remain isolated from the build environment. This leakage of private information can compromise entire development infrastructures, expose intellectual property, and potentially provide attackers with additional attack vectors for further system compromise. The vulnerability particularly affects organizations relying on Open Build Service for automated package building, where the build workers may have access to sensitive corporate or personal data.
This vulnerability aligns with CWE-59, which describes improper handling of symbolic links, specifically the weakness of following symbolic links without proper validation. The issue also maps to ATT&CK technique T1059, where adversaries leverage build systems and development environments to access sensitive files through legitimate system processes. Organizations should implement immediate mitigations including updating to Open Build Service version 20170320 or later, where the symbolic link handling has been properly restricted. Additional protective measures include implementing strict filesystem permissions for build directories, monitoring symbolic link creation during build processes, and establishing automated scanning for potentially malicious link structures. System administrators should also consider implementing containerization or virtualization of build environments to further isolate potential impacts from such vulnerabilities.