CVE-2017-5646 in KNOX
Summary
by MITRE
For versions of Apache Knox from 0.2.0 to 0.11.0 - an authenticated user may use a specially crafted URL to impersonate another user while accessing WebHDFS through Apache Knox. This may result in escalated privileges and unauthorized data access. While this activity is audit logged and can be easily associated with the authenticated user, this is still a serious security issue. All users are recommended to upgrade to the Apache Knox 0.12.0 release.
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Analysis
by VulDB Data Team • 05/27/2017
The vulnerability identified as CVE-2017-5646 represents a critical authorization bypass flaw within Apache Knox versions ranging from 0.2.0 through 0.11.0. This issue specifically affects the WebHDFS gateway functionality where authenticated users can exploit a crafted URL mechanism to impersonate other users within the system. The vulnerability stems from improper validation of user identities during WebHDFS operations, creating a pathway for privilege escalation and unauthorized data access. The flaw operates at the application layer and leverages the trust relationship between the gateway and underlying Hadoop services, making it particularly dangerous in enterprise environments where data security is paramount.
The technical implementation of this vulnerability involves a specific URL manipulation technique that allows an authenticated user to construct requests that appear to originate from different user accounts. This occurs due to insufficient user context validation within the Knox gateway's WebHDFS proxy implementation. The flaw is categorized under CWE-285 - Improper Authorization, which specifically addresses scenarios where systems fail to properly verify that the entity making a request has the necessary permissions. The vulnerability operates through the gateway's request routing mechanism, where user identity information is not adequately validated or sanitized before being forwarded to the target WebHDFS service. This creates a situation where legitimate authenticated users can manipulate their session context to access resources that should be restricted to other users.
From an operational impact perspective, this vulnerability enables attackers with valid credentials to escalate their privileges and gain unauthorized access to sensitive data that should be restricted to specific user groups or individuals. The attack vector requires only an authenticated user account, making it particularly dangerous as it can be exploited by insiders or compromised accounts. While the system does maintain audit logs that associate the malicious activity with the authenticated user who initiated the attack, this logging capability does not prevent the unauthorized access from occurring. The vulnerability affects the integrity and confidentiality of data stored within Hadoop clusters that rely on Knox for gateway services, potentially exposing sensitive information to unauthorized parties. This issue directly impacts the principle of least privilege and can lead to significant data breaches in environments where Knox serves as a critical access control mechanism.
Organizations affected by this vulnerability should immediately implement the recommended mitigation strategy of upgrading to Apache Knox version 0.12.0 or later, which contains the necessary patches to address the authorization bypass. The upgrade process should be carefully planned and tested in non-production environments to ensure compatibility with existing configurations and applications. Additional defensive measures include implementing network-level restrictions to limit access to Knox gateway endpoints, enhancing monitoring of audit logs for suspicious URL patterns, and conducting comprehensive security assessments of all WebHDFS access points. Security teams should also consider implementing additional authentication controls and access reviews to identify any potential unauthorized access that may have occurred during the vulnerability window. The ATT&CK framework categorizes this issue under privilege escalation techniques, specifically involving the use of valid accounts to gain access to additional resources, making it relevant to both defensive and offensive security operations. Organizations should also review their incident response procedures to ensure readiness for potential exploitation of this vulnerability and maintain awareness of similar authorization bypass issues that may affect other components of their Hadoop ecosystem.