Key points
- The flaw affects versions of the SAP Cloud SDK for Python prior to 0.45.2.
- Attackers exploit the tenant_subdomain parameter to redirect OAuth2 token requests to malicious servers.
- The NVD records the issue as CVE-2026-89111 with a CVSS score of 10, classified as critical.
The short version
- The SAP Cloud SDK for Python contains a severe security flaw in its OAuth2 implementation.
- An attacker controlling the tenant_subdomain parameter can force the application to send tokens to their server.
- This results in the exfiltration of sensitive client credentials from multi-tenant BTP applications.
The details
The National Vulnerability Database has recorded CVE-2026-89111 as a critical vulnerability affecting the SAP Cloud SDK for Python. According to the NVD record, the issue carries a CVSS score of 10, placing it at the highest level of severity. The flaw stems from weaknesses identified under CWE-918, which relates to server-side request forgery. This specific implementation error exists within the OAuth2 handling components of the library.
The vulnerability specifically impacts multi-tenant applications built on the SAP Business Technology Platform (BTP). The core mechanism of the attack involves the manipulation of the tenant_subdomain parameter. An attacker who can control or influence this parameter is able to redirect OAuth2 token requests. Instead of the requests reaching the legitimate authentication server, they are sent to a server controlled by the attacker.
This redirection allows the malicious party to intercept the data flow. The primary consequence described in the source material is the exfiltration of client credentials. When the application attempts to obtain or refresh tokens, the sensitive authentication details are transmitted to the attacker’s endpoint. This compromise undermines the security of the application’s identity management and access controls.
The context
The affected software is the SAP Cloud SDK for Python, specifically any version below 0.45.2. According to the NVD data, the product is listed under SAP SE. The vulnerability highlights the risks associated with server-side request forgery in cloud development kits. By trusting user-supplied input for internal network requests, the SDK inadvertently created a path for credential theft.
This issue is particularly relevant for developers and organisations deploying multi-tenant architectures on the BTP. Such environments often handle data from multiple customers, making the protection of client credentials paramount. The ability to hijack token requests at this level suggests a breakdown in the trust model of the SDK’s network requests.
Defender's checklist
Security teams should audit their Python-based applications for dependencies on the SAP Cloud SDK. Any project using a version older than 0.45.2 is considered at risk according to the NVD. Developers must verify that the tenant_subdomain parameter is not influenced by untrusted external inputs. Monitoring network logs for unexpected OAuth2 request destinations can help detect active exploitation of this flaw.
What to do and how to stay safe: SAP
- Review all Python projects for the presence of the SAP Cloud SDK and check the installed version number.
- Ensure that any version of the SDK prior to 0.45.2 is upgraded immediately to patch the known vulnerability.
- Implement strict input validation for the tenant_subdomain parameter to prevent manipulation by external actors.
- Monitor server logs for unusual outbound connections to unfamiliar domains during OAuth2 authentication flows.
Step-by-step guide: Unpatched Software: Why Missing Updates Create Hidden Entry Points
General security guidance from the Cipher Insider newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
Which versions of the SAP Cloud SDK for Python are vulnerable?
According to the NVD, all versions of the SAP Cloud SDK for Python prior to 0.45.2 are affected by this vulnerability.
What is the technical root cause of the credential leak?
The flaw is a server-side request forgery (CWE-918) where the tenant_subdomain parameter redirects OAuth2 token requests to an attacker-controlled server.
Is this vulnerability currently being exploited in the wild?
The source material does not state whether the vulnerability is currently being exploited in the wild, only that it allows for credential exfiltration.
