CVE-2017-18037 in Bitbucket Server
Summary
by MITRE
The git repository tag rest resource in Atlassian Bitbucket Server from version 3.7.0 before 4.14.11 (the fixed version for 4.14.x), from version 5.0.0 before 5.0.9 (the fixed version for 5.0.x), from version 5.1.0 before 5.1.8 (the fixed version for 5.1.x), from version 5.2.0 before 5.2.6 (the fixed version for 5.2.x), from version 5.3.0 before 5.3.4 (the fixed version for 5.3.x), from version 5.4.0 before 5.4.2 (the fixed version for 5.4.x), from version 5.5.0 before 5.5.1 (the fixed version for 5.5.x) and before 5.6.0 allows remote attackers to read arbitrary files via a path traversal vulnerability through the name of a git tag.
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Analysis
by VulDB Data Team • 01/01/2020
The vulnerability identified as CVE-2017-18037 represents a critical path traversal flaw in Atlassian Bitbucket Server's git repository tag resource handling mechanism. This vulnerability exists in multiple version ranges across different major releases, indicating a persistent security issue that affected the platform from version 3.7.0 through 5.5.1. The flaw specifically manifests in the REST API endpoint responsible for handling git tag operations, where improper input validation allows malicious actors to manipulate file paths and access unauthorized system resources. The vulnerability stems from insufficient sanitization of user-supplied tag names that are processed through the git repository interface, creating an attack surface where arbitrary file reads can be executed remotely.
This path traversal vulnerability operates by exploiting the way Bitbucket Server processes git tag names through its REST API endpoints. When a git tag name is provided as part of a request to the repository tag resource, the system fails to properly validate or sanitize the input before using it in file system operations. Attackers can craft malicious tag names containing directory traversal sequences such as ../ or ..\ that bypass normal access controls and allow them to navigate outside the intended repository boundaries. The flaw specifically affects the git tag name parameter, which is used in the context of repository operations, making it possible for remote attackers to access files anywhere on the server filesystem that the Bitbucket process has permissions to read.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the ability to access sensitive files that may contain configuration data, authentication credentials, or other confidential information stored on the server. The vulnerability affects all versions of Bitbucket Server within the specified ranges, with different fixed versions available for each major release line, demonstrating that this was a widespread issue affecting multiple generations of the product. Organizations running affected versions are at risk of data breaches, as the vulnerability allows for arbitrary file reading without authentication, potentially exposing source code repositories, system configuration files, and other sensitive artifacts. The impact is particularly severe in environments where Bitbucket Server hosts proprietary code or contains sensitive organizational data.
Security practitioners should immediately implement mitigations for this vulnerability by upgrading to the patched versions mentioned in the advisory, which are 4.14.11 for 4.14.x, 5.0.9 for 5.0.x, 5.1.8 for 5.1.x, 5.2.6 for 5.2.x, 5.3.4 for 5.3.x, 5.4.2 for 5.4.x, and 5.5.1 for 5.5.x. Organizations should also consider implementing network-level restrictions to limit access to the Bitbucket REST API endpoints, particularly those related to git repository operations. The vulnerability aligns with CWE-22 Path Traversal and maps to ATT&CK technique T1083 File and Directory Discovery, as attackers can systematically enumerate and access files on the compromised system. Additionally, organizations should conduct thorough security assessments of their Bitbucket Server installations to ensure that no unauthorized access has occurred, and implement monitoring for suspicious API access patterns that may indicate exploitation attempts.