CVE-2017-8040 in Single Sign-On
Summary
by MITRE
In Single Sign-On for Pivotal Cloud Foundry (PCF) 1.3.x versions prior to 1.3.4 and 1.4.x versions prior to 1.4.3, an XXE (XML External Entity) attack was discovered in the Single Sign-On service dashboard. Privileged users can in some cases upload malformed XML leading to exposure of data on the Single Sign-On service broker file system.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 11/14/2019
The vulnerability identified as CVE-2017-8040 represents a critical XML External Entity injection flaw within the Single Sign-On service dashboard of Pivotal Cloud Foundry platforms. This weakness specifically affects PCF versions 1.3.x before 1.3.4 and 1.4.x before 1.4.3, creating a pathway for attackers to exploit the system through malformed XML uploads. The vulnerability resides in the service broker component that handles XML processing, making it particularly dangerous as it targets the core authentication infrastructure that governs user access across the platform. Such a flaw fundamentally undermines the security posture of organizations relying on PCF for their cloud infrastructure, as it provides a potential entry point for unauthorized access to sensitive authentication data and system resources.
The technical implementation of this vulnerability stems from insufficient input validation within the XML parsing mechanisms of the SSO service dashboard. When privileged users upload malformed XML content, the system processes these entities without proper sanitization, allowing external entity references to be resolved and potentially exposing internal file system contents. This XXE attack vector operates at the application layer and can be leveraged to read local files, perform port scanning, or even execute remote code depending on the underlying system configuration. The attack requires minimal privileges to initiate, as the vulnerability specifically targets the dashboard interface where administrative users typically interact with the service broker functionality. This makes the exploit particularly dangerous as it can be initiated by users with relatively low-level access who have been granted dashboard permissions, potentially leading to escalation of privileges or data exfiltration.
The operational impact of CVE-2017-8040 extends far beyond simple data exposure, as it compromises the fundamental authentication mechanisms that protect cloud infrastructure. Organizations utilizing affected PCF versions face potential unauthorized access to sensitive user credentials, authentication tokens, and system configuration files that could be used to escalate privileges or launch further attacks against the broader cloud environment. The vulnerability's presence in the Single Sign-On service creates cascading security risks, as compromise of this component can lead to unauthorized access to multiple applications and services that rely on the platform's authentication infrastructure. This risk is particularly severe in enterprise environments where PCF serves as a central platform for application deployment and user management, potentially exposing thousands of users to credential theft or service disruption. The attack surface is further expanded by the fact that the vulnerability can be exploited through the web interface, making it accessible to attackers with minimal technical expertise.
Mitigation strategies for CVE-2017-8040 require immediate implementation of version updates to PCF 1.3.4 or 1.4.3, which contain the necessary patches to address the XXE vulnerability. Organizations should also implement strict input validation and sanitization measures within their XML processing components, ensuring that all external entity references are properly disabled or restricted. Network segmentation and access controls should be enhanced to limit exposure of the SSO service dashboard to only authorized users, while comprehensive monitoring should be implemented to detect suspicious XML upload activities. Security teams should conduct thorough vulnerability assessments of all PCF installations and related services to identify potential additional XXE vulnerabilities within the platform. The remediation process should include comprehensive testing of the patched versions to ensure that no regression issues affect core platform functionality, while also implementing security awareness training for administrators to recognize potential exploitation attempts. This vulnerability aligns with CWE-611, which specifically addresses XML External Entity processing without proper restrictions, and maps to ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting through web application attacks. Organizations should also consider implementing Web Application Firewalls and additional logging mechanisms to provide visibility into XML processing activities and potential exploitation attempts.