OAuth2 SSRF vulnerability in SAP Cloud SDK for Python

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.

This vulnerability was originally fixed in 0.45.2. It was reintroduced in 0.53.0 when the HTTP client was refactored into a shared core module, and the tenant subdomain validation was not carried over to the new location. The validation was restored in 0.55.1.