CVE-2019-3876 in OAuth Server
Summary
by MITRE
A flaw was found in the /oauth/token/request custom endpoint of the OpenShift OAuth server allowing for XSS generation of CLI tokens due to missing X-Frame-Options and CSRF protections. If not otherwise prevented, a separate XSS vulnerability via JavaScript could further allow for the extraction of these tokens.
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Analysis
by VulDB Data Team • 08/21/2023
The vulnerability identified as CVE-2019-3876 resides within the OpenShift OAuth server's custom endpoint implementation, specifically the /oauth/token/request path that handles command line interface token generation. This flaw represents a critical security weakness that undermines the integrity of the authentication system by failing to implement essential web security controls. The OpenShift platform, which serves as a container application platform built on top of Kubernetes, relies heavily on secure authentication mechanisms to protect cluster access and resource management operations. When an attacker can exploit this vulnerability, they gain the ability to manipulate the token generation process and potentially compromise the entire platform's security posture.
The technical root cause of this vulnerability stems from the absence of proper security headers and cross-site request forgery protections within the OAuth token endpoint. The missing X-Frame-Options header leaves the endpoint vulnerable to clickjacking attacks where malicious actors can embed the token request interface within hidden iframes to capture user interactions. Additionally, the lack of CSRF protection mechanisms means that unauthorized parties can forge requests to the token endpoint, potentially generating tokens on behalf of authenticated users without their knowledge or consent. This vulnerability aligns with CWE-352, which describes Cross-Site Request Forgery weaknesses, and CWE-1021, which addresses Improper Restriction of Rendered UI Layers or Frames. The flaw essentially creates an attack surface where malicious actors can exploit the trust relationship between the browser and the OAuth server to execute unauthorized token generation requests.
The operational impact of CVE-2019-3876 extends beyond simple token generation manipulation and represents a significant threat to cluster security and access control. An attacker who successfully exploits this vulnerability could obtain valid CLI tokens that would grant them full administrative access to the OpenShift cluster, including the ability to deploy applications, manage resources, and potentially escalate privileges within the containerized environment. The vulnerability becomes particularly dangerous when combined with other XSS weaknesses, as demonstrated in the original description where JavaScript-based attacks could extract these tokens from the browser's memory or storage. This creates a cascading security risk where the initial XSS vulnerability serves as a vector to harvest authentication tokens, enabling persistent unauthorized access. The implications are severe for organizations relying on OpenShift for production workloads, as compromised tokens could lead to data breaches, service disruption, and unauthorized resource consumption.
Mitigation strategies for CVE-2019-3876 must address both the immediate security gaps and implement comprehensive protection measures for the OAuth server components. Organizations should immediately implement the missing X-Frame-Options header with appropriate values such as SAMEORIGIN or DENY to prevent clickjacking attacks. The implementation of robust CSRF protection mechanisms, including the use of anti-forgery tokens and proper request validation, should be enforced at the token endpoint level. Security headers should be configured to include Content Security Policy directives that restrict frame embedding and script execution. Additionally, organizations should implement proper input validation and sanitization for all parameters accepted by the OAuth endpoints, following the principle of least privilege for token generation requests. The ATT&CK framework categorizes this vulnerability under T1548.001 for Abuse of Cloud Infrastructure and T1078 for Valid Accounts, highlighting the need for both network-level protections and account monitoring to detect unauthorized token usage. Regular security assessments and penetration testing should be conducted to verify that all authentication endpoints properly implement security controls, with particular attention to custom OAuth implementations that may bypass standard security protections.