CVE-2017-18038 in Bitbucket Server
Summary
by MITRE
The repository settings resource in Atlassian Bitbucket Server before version 5.6.0 allows remote attackers to read the first line of arbitrary files via a path traversal vulnerability through the default branch name.
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Analysis
by VulDB Data Team • 01/01/2020
The vulnerability identified as CVE-2017-18038 represents a critical path traversal flaw within Atlassian Bitbucket Server's repository settings resource functionality. This vulnerability exists in versions prior to 5.6.0 and enables remote attackers to access sensitive information by reading the first line of arbitrary files on the server. The vulnerability specifically leverages the default branch name parameter within the repository settings API endpoint, creating an opportunity for unauthorized data extraction from the underlying file system.
The technical exploitation of this vulnerability occurs through a carefully crafted request that manipulates the default branch name parameter to traverse file system paths. Attackers can construct malicious requests that bypass normal access controls and retrieve the first line of files that should otherwise remain protected. This path traversal mechanism allows adversaries to potentially access configuration files, credential storage locations, or other sensitive data that may be stored within the repository's file system structure. The vulnerability falls under the CWE-22 category for Path Traversal and aligns with ATT&CK technique T1213.002 for Data from Information Repositories.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can lead to unauthorized access to sensitive system components that may contain authentication credentials, configuration settings, or other valuable data. Attackers who successfully exploit this vulnerability can gain insights into the system's internal structure and potentially escalate their privileges by accessing files that contain sensitive information. The exposure of the first line of arbitrary files creates a significant risk for organizations that store sensitive data within their repository environments, as even partial information disclosure can aid in further attacks against the system.
Organizations using affected versions of Bitbucket Server should immediately implement mitigations including upgrading to version 5.6.0 or later, which contains the necessary patches to address this vulnerability. Additional protective measures include implementing network segmentation to limit access to repository servers, configuring proper access controls and authentication mechanisms, and monitoring for suspicious API requests that may indicate exploitation attempts. The vulnerability demonstrates the importance of input validation and proper parameter handling in web applications, particularly when dealing with user-supplied data that may be used to construct file system paths or API requests. Security teams should also consider implementing web application firewalls and intrusion detection systems to monitor for exploitation patterns associated with path traversal attacks.