CVE-2019-3787 in Cloud Foundry UAA
Summary
by MITRE
Cloud Foundry UAA, versions prior to 73.0.0, falls back to appending ?unknown.org? to a user's email address when one is not provided and the user name does not contain an @ character. This domain is held by a private company, which leads to attack vectors including password recovery emails sent to a potentially fraudulent address. This would allow the attacker to gain complete control of the user's account.
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Analysis
by VulDB Data Team • 10/07/2023
The vulnerability identified as CVE-2019-3787 affects Cloud Foundry User Account and Authentication (UAA) systems operating in versions prior to 73.0.0, representing a critical authentication flaw that directly impacts user account security. This issue stems from the UAA service's improper handling of user registration scenarios where email addresses are not provided during account creation. When a user attempts to register without supplying an email address and their username lacks an @ character, the system automatically appends the domain ?unknown.org? to create a pseudo-email address. This fallback mechanism, while seemingly benign, creates a significant security weakness that can be exploited by malicious actors to compromise user accounts.
The technical flaw in this vulnerability resides in the lack of proper input validation and sanitization within the user registration process. According to CWE-20, this represents a weakness involving improper input validation, specifically in how the system handles missing or malformed user data. The UAA service fails to implement robust validation that would either require a valid email address during registration or properly handle cases where email information is missing. This behavior creates a predictable and exploitable pattern where attackers can manipulate the system to generate email addresses under the control of a third-party domain holder, effectively bypassing normal email-based security controls such as password recovery mechanisms.
The operational impact of this vulnerability extends far beyond simple account compromise, creating multiple attack vectors that can lead to complete system infiltration. An attacker who discovers this behavior can register accounts using the ?unknown.org? domain and subsequently exploit the password recovery process to gain access to legitimate user accounts. This attack pattern aligns with techniques described in the MITRE ATT&CK framework under T1566 for credential harvesting and T1078 for valid accounts. The vulnerability essentially allows for account takeover attacks where malicious actors can intercept password reset emails sent to the fabricated ?unknown.org? addresses, thereby gaining unauthorized access to user accounts and potentially accessing sensitive organizational data or system resources.
The implications of this vulnerability are particularly severe in enterprise environments where Cloud Foundry UAA services manage authentication for multiple applications and users. Organizations relying on these systems for identity management face significant risks including unauthorized data access, privilege escalation, and potential lateral movement within their network infrastructure. The issue also undermines the trust model of the authentication system, as users may receive password reset emails at unexpected addresses, potentially leading to credential compromise without proper user awareness. Organizations should consider this vulnerability as part of a broader authentication security posture assessment, particularly focusing on email-based recovery mechanisms and the handling of incomplete user registration data.
The recommended mitigation strategy involves upgrading to Cloud Foundry UAA version 73.0.0 or later, which implements proper email validation and prevents the automatic appending of the ?unknown.org? domain. Additionally, organizations should implement strict email validation policies during user registration, requiring valid email addresses or implementing proper fallback mechanisms that do not rely on third-party domains. Security teams should also monitor for unauthorized account registrations and implement additional authentication controls such as multi-factor authentication to reduce the impact of potential account takeovers. The vulnerability serves as a reminder of the importance of proper input validation and the need for robust security controls in authentication systems, particularly when handling user data and email addresses.