The RedirectHandler middleware in microsoft/kiota-java (com.microsoft.kiota:microsoft-kiota-http-okHttp v1.9.0) and other Kiota libraries fails to strip sensitive HTTP headers when following 3xx redirects to a different host or scheme. Only the Authorization header is removed; Cookie, Proxy-Authorization, and all custom headers are forwarded to the redirect target.

Kiota is an OpenAPI based HTTP Client code generator. Versions prior to 1.31.1 are affected by a code-generation literal injection vulnerability in multiple writer sinks (for example: serialization/deserialization keys, path/query parameter mappings, URL template metadata, enum/property metadata, and default value emission). When malicious values from an OpenAPI description are emitted into generated source without context-appropriate escaping, an attacker can break out of string literals and inject additional code into generated clients. This issue is only practically exploitable when the OpenAPI description used for generation is from an untrusted source, or a normally trusted OpenAPI description has been compromised/tampered with. Only generating from trusted, integrity-protected API descriptions significantly reduces the risk. To remediate the issue, upgrade Kiota to 1.31.1 or later and regenerate/refresh existing generated clients as a precaution. Refreshing generated clients ensures previously generated vulnerable code is replaced with hardened output.