CVE-2017-16858 in Crowd
Summary
by MITRE
The 'crowd-application' plugin module (notably used by the Google Apps plugin) in Atlassian Crowd from version 1.5.0 before version 3.1.2 allowed an attacker to impersonate a Crowd user in REST requests by being able to authenticate to a directory bound to an application using the feature. Given the following situation: the Crowd application is bound to directory 1 and has a user called admin and the Google Apps application is bound to directory 2, which also has a user called admin, it was possible to authenticate REST requests using the credentials of the user coming from directory 2 and impersonate the user from directory 1.
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Analysis
by VulDB Data Team • 12/31/2019
The vulnerability identified as CVE-2017-16858 represents a critical authentication bypass flaw within Atlassian Crowd's plugin architecture that undermines the fundamental security boundaries between directory services. This issue specifically affects the crowd-application plugin module, which serves as a bridge between Crowd and various applications including the widely used Google Apps plugin. The vulnerability stems from a design flaw in how Crowd handles user authentication when multiple directories are bound to different applications, creating an unintended pathway for privilege escalation and identity impersonation attacks.
The technical flaw manifests through improper session management and authentication token handling within the REST API endpoints of the Crowd application. When a Crowd application is configured to connect to multiple directories, the system fails to properly validate the source directory of authenticated users during REST requests. This allows an attacker to leverage credentials from one directory to authenticate against a different directory's application, effectively bypassing the intended directory isolation mechanisms. The vulnerability specifically exploits the lack of proper directory context verification during authentication processes, enabling cross-directory impersonation attacks.
The operational impact of this vulnerability is severe and multifaceted, as it can lead to unauthorized access to sensitive systems and data. Attackers can exploit this flaw to impersonate legitimate users from different directories, potentially gaining access to applications and resources that should be restricted to specific user groups. In the described scenario where directory 1 contains an admin user and directory 2 also contains an admin user, an attacker could authenticate using directory 2 credentials to access directory 1 resources, effectively elevating their privileges and bypassing security controls. This vulnerability particularly affects organizations that rely on multiple directory services within their Crowd infrastructure, as it undermines the security model of directory separation and user isolation.
Organizations should implement immediate mitigations including upgrading to Atlassian Crowd version 3.1.2 or later, which contains the necessary patches to address the authentication bypass vulnerability. Additional protective measures include implementing strict access controls and monitoring for unusual authentication patterns, particularly cross-directory authentication attempts. Security teams should also review and audit existing Crowd configurations to ensure proper directory isolation and implement network-level controls to restrict unauthorized access to Crowd REST endpoints. The vulnerability aligns with CWE-287, which addresses improper authentication issues, and maps to ATT&CK technique T1078.004 for valid accounts and T1550.001 for use of stolen credentials, highlighting the need for comprehensive security monitoring and access control measures.
This vulnerability demonstrates the critical importance of proper authentication context validation in multi-directory systems and underscores the risks associated with insufficient session management in enterprise authentication platforms. The flaw represents a classic case of inadequate input validation and authentication boundary enforcement, where the system fails to maintain proper security contexts when transitioning between different directory services. Organizations should also consider implementing additional security controls such as multi-factor authentication, enhanced logging, and regular security assessments to prevent exploitation of similar authentication bypass vulnerabilities in their infrastructure.