CVE-2017-18088 in Bitbucket Server
Summary
by MITRE
Various plugin servlet resources in Atlassian Bitbucket Server before version 5.3.7 (the fixed version for 5.3.x), from version 5.4.0 before 5.4.6 (the fixed version for 5.4.x), from version 5.5.0 before 5.5.6 (the fixed version for 5.5.x), from version 5.6.0 before 5.6.3 (the fixed version for 5.6.x), from version 5.7.0 before 5.7.1 (the fixed version for 5.7.x) and before 5.8.0 allow remote attackers to conduct clickjacking attacks via framing various resources that lacked clickjacking protection.
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Analysis
by VulDB Data Team • 01/06/2020
The vulnerability described in CVE-2017-18088 represents a critical web application security flaw in Atlassian Bitbucket Server that enables remote attackers to execute clickjacking attacks through improperly configured servlet resources. This vulnerability affects multiple version ranges across the 5.3.x through 5.7.x release lines, with specific fixed versions identified for each major branch. The issue stems from the absence of proper clickjacking protection mechanisms in various plugin servlet resources, creating a significant risk for organizations relying on Bitbucket Server for version control and collaboration. The vulnerability is classified under CWE-1021, which specifically addresses insufficient protection against clickjacking attacks in web applications. Clickjacking attacks occur when malicious actors embed legitimate web applications within hidden iframes to trick users into performing unintended actions, making this a particularly dangerous security flaw in collaborative development environments where users frequently interact with web interfaces.
The technical implementation of this vulnerability involves the lack of proper Content Security Policy (CSP) headers and X-Frame-Options directives in the affected servlet resources. When Bitbucket Server serves these plugin servlets without adequate framing protection, attackers can create malicious web pages that overlay legitimate Bitbucket interfaces with invisible or disguised elements. Users visiting these crafted pages may unknowingly perform actions such as committing code changes, modifying repository permissions, or accessing sensitive administrative functions while believing they are interacting with legitimate Bitbucket interfaces. The flaw affects various plugin servlet resources throughout the application's architecture, making it particularly challenging to secure comprehensively since multiple attack vectors exist within the same application framework. This vulnerability directly aligns with ATT&CK technique T1211, which describes the use of malicious web content to manipulate user interactions through framing techniques. The absence of frame-busting code and proper security headers creates an environment where attackers can exploit user trust in legitimate applications to execute unauthorized operations.
The operational impact of this vulnerability extends beyond simple unauthorized access to potentially compromising entire development workflows and source code repositories. Organizations using affected Bitbucket Server versions face significant risks including unauthorized code modifications, data integrity violations, and potential exposure of sensitive source code. The vulnerability's scope across multiple minor versions suggests a systemic issue in the application's security hardening approach, indicating that developers may have overlooked consistent implementation of clickjacking protection mechanisms. Attackers can leverage this vulnerability to manipulate user sessions, perform privilege escalation attacks, or harvest credentials from unsuspecting users who interact with maliciously crafted web pages. The attack vector is particularly concerning in enterprise environments where Bitbucket Server serves as a central hub for software development and collaboration, as successful exploitation could lead to complete compromise of development infrastructure. Security teams must consider the potential for cascading effects where compromised Bitbucket instances could serve as entry points for broader network infiltration, making this vulnerability particularly dangerous in complex organizational environments.
Organizations should immediately implement mitigations including updating to the fixed versions specified for each affected release line, typically requiring patch management processes that include thorough testing in staging environments before production deployment. The recommended approach involves ensuring all plugin servlet resources implement proper X-Frame-Options headers with values such as SAMEORIGIN or DENY, along with comprehensive Content Security Policy implementations that prevent framing of application resources. Network-level protections such as web application firewalls and security monitoring systems should be configured to detect and block suspicious framing attempts. Security teams should conduct comprehensive vulnerability assessments to identify any additional servlet resources that may lack proper clickjacking protection beyond the explicitly mentioned plugin components. The remediation process should include implementing automated security scanning tools that can detect missing security headers and frame protection mechanisms. Additionally, user education programs should emphasize the importance of avoiding suspicious web content and verifying the legitimacy of web pages before interacting with them, particularly in environments where Bitbucket Server is extensively used for collaborative development activities.