CVE-2026-89111 in Cloud SDK
Summary
by MITRE • 10/13/2026
The SAP Cloud SDK for Python contains an OAuth2 SSRF vulnerability affecting multi-tenant BTP applications. An attacker who controls the tenant_subdomain parameter can redirect OAuth2 token requests to an attacker-controlled server, causing client credentials to be exfiltrated.
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Analysis
by VulDB Data Team • 10/13/2026
The identified security flaw resides within the SAP Cloud SDK for Python and specifically impacts multi-tenant Business Technology Platform (BTP) applications that utilize OAuth 2.0 authentication flows. This vulnerability is classified as a Server-Side Request Forgery, commonly referred to by its CWE identifier CWE-918. The core technical issue stems from insufficient validation of user-supplied input within the tenant_subdomain parameter used during the token request process. In a multi-tenant architecture, this parameter dictates which identity provider or authorization server should be contacted to validate credentials and issue access tokens. When an attacker gains control over this specific parameter, they can manipulate the internal logic of the SDK to redirect the outgoing HTTP requests intended for legitimate OAuth 2.0 endpoints toward servers under their own control. This redirection bypasses standard security checks because the application trusts the tenant_subdomain value as a valid destination without verifying its integrity or ensuring it belongs to an authorized domain list.
The operational impact of this vulnerability is severe, primarily centering on credential theft and potential unauthorized access to sensitive resources. By successfully redirecting OAuth 2.0 token requests, an attacker can intercept client credentials such as secrets, tokens, or authorization codes that are transmitted during the authentication handshake. Once these credentials are exfiltrated to the attacker-controlled server, they can be used to impersonate legitimate users or services within the BTP environment. This leads directly to a breach of confidentiality and integrity for the affected application's data and infrastructure. Furthermore, if the stolen tokens possess elevated privileges, the attacker may escalate their access rights, potentially gaining control over backend systems, databases, or other microservices connected to the compromised tenant context.
From an offensive security perspective, this vulnerability aligns with MITRE ATT&CK technique T1557, which covers Adversary-in-the-Middle scenarios where attackers intercept communication between two parties. The exploitation path typically involves crafting a malicious request that includes a specially crafted tenant_subdomain value pointing to a domain controlled by the attacker. When the application processes this request, it initiates an outbound connection to the malicious server instead of the legitimate identity provider. This allows the attacker to capture sensitive authentication data in transit without triggering immediate alarms from standard network security controls designed to detect external threats rather than internal logic flaws.
To mitigate this vulnerability, developers must implement strict input validation and allowlisting mechanisms for all parameters that influence outbound request destinations. Specifically, the tenant_subdomain parameter should be validated against a predefined list of trusted domains or patterns associated with legitimate identity providers within the BTP landscape. Additionally, implementing DNS rebinding protections and ensuring that internal services do not process external inputs as direct targets for network requests are critical defensive measures. Upgrading to patched versions of the SAP Cloud SDK for Python is essential if available, as these updates typically include rigorous sanitization logic. Security teams should also monitor outbound traffic from application servers for anomalies in domain resolution patterns, particularly those involving unexpected or newly registered domains during authentication flows.