CVE-2018-5225 in Bitbucket Server
Summary
by MITRE
In browser editing in Atlassian Bitbucket Server from version 4.13.0 before 5.4.8 (the fixed version for 4.13.0 through 5.4.7), 5.5.0 before 5.5.8 (the fixed version for 5.5.x), 5.6.0 before 5.6.5 (the fixed version for 5.6.x), 5.7.0 before 5.7.3 (the fixed version for 5.7.x), and 5.8.0 before 5.8.2 (the fixed version for 5.8.x), allows authenticated users to gain remote code execution using the in browser editing feature via editing a symbolic link within a repository.
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Analysis
by VulDB Data Team • 01/15/2020
This vulnerability exists within Atlassian Bitbucket Server's browser editing functionality, specifically affecting versions from 4.13.0 through 5.8.1 across multiple release branches. The flaw represents a critical security issue that allows authenticated users to execute arbitrary code remotely through a sophisticated attack vector involving symbolic link manipulation. The vulnerability stems from insufficient input validation and improper handling of file system operations within the browser-based repository editing interface. Attackers can exploit this by creating or modifying symbolic links within repository contents, which then get processed by the server with elevated privileges, bypassing normal access controls and file system restrictions.
The technical implementation of this vulnerability leverages the browser editing feature's inability to properly sanitize or validate symbolic link references during file operations. When users edit repository content through the web interface, the system processes these operations without adequate verification of file system metadata, particularly around symbolic link resolution. This creates a path traversal scenario where maliciously crafted symbolic links can point to arbitrary system locations, allowing attackers to execute code in the context of the Bitbucket Server process. The vulnerability is classified under CWE-352 as Cross-Site Request Forgery, though its exploitation mechanism is more accurately described as a privilege escalation through insecure file handling. The attack requires authentication but does not need administrative privileges, making it particularly dangerous as it can be exploited by any authenticated user with repository access.
The operational impact of CVE-2018-5225 is severe and multifaceted, potentially allowing attackers to completely compromise Bitbucket Server instances and gain persistent access to source code repositories. Successful exploitation enables attackers to execute arbitrary commands on the server, potentially leading to data exfiltration, code modification, or further network compromise. The vulnerability affects organizations using Bitbucket Server for code management, making it a prime target for attackers seeking to access sensitive source code, development environments, or corporate intellectual property. The attack surface extends beyond immediate code execution to include potential privilege escalation, lateral movement within networks, and data theft from version-controlled repositories. Organizations with multiple Bitbucket Server instances or those using older versions without proper patching are particularly vulnerable to this attack vector, which can be exploited through standard user accounts without requiring special administrative access.
Mitigation strategies for this vulnerability include immediate patching of affected Bitbucket Server versions to the recommended fixed releases, specifically versions 5.4.8, 5.5.8, 5.6.5, 5.7.3, and 5.8.2. Organizations should implement network segmentation and access controls to limit exposure of Bitbucket Server instances to untrusted networks. The principle of least privilege should be enforced by restricting user permissions and ensuring that only authorized personnel have access to repository editing functionality. Additional protective measures include implementing web application firewalls to monitor for suspicious file operations and establishing regular security audits of repository contents. Organizations should also consider disabling browser-based editing features if they are not essential to their workflow, particularly in high-security environments. The vulnerability aligns with ATT&CK technique T1059.001 for command and script injection, and T1078 for valid accounts, as it exploits authenticated user access to execute malicious operations. Regular vulnerability assessments and security monitoring should be implemented to detect potential exploitation attempts and ensure that all systems remain protected against similar attack vectors.