Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.5, Kiota resolved OpenAPI $ref values by fetching remote http(s) URLs and reading local absolute or out-of-tree file paths, allowing `kiota generate` on an attacker-controlled or attacker-influenced description to perform build-time SSRF, remote file inclusion, and local file inclusion by inlining external schemas such as REMOTE_KIOTA_PROP or Leaked into generated clients. This issue is fixed in version 1.29.1 and 1.32.5 by AllowedExternalOriginsStreamLoader and the --allowed-external-origins option.
Affected: NuGet: Microsoft.OpenApi.Kiota, NuGet: Microsoft.OpenApi.Kiota.Builder
## Summary
Microsoft Kiota resolved OpenAPI `$ref`s by fetching remote `http(s)` URLs and reading local files (including absolute / out-of-tree paths), inlining the referenced schema into the generated client. Running `kiota generate` on a spec whose `$ref` pointed at an attacker/internal URL or an arbitrary local file yielded SSRF, remote file inclusion, and local file inclusion. Verified on **1.32.3 / 1.32.4**.
### Details
- `$ref: http://attacker/internal-evil.json#/...` → build host fetches the URL (SSRF) and inlines the remote schema (RFI); confirmed property `REMOTE_KIOTA_PROP` in the generated client. - `$ref: /abs/path.json#/...` or `../../secret.json#/...` → Kiota reads the out-of-tree local file and inlines its schema (LFI); confirmed `Leaked` schema in the generated client. Resolution is transitive across nesting levels.
Kiota **escapes** its output sinks (comments/strings/identifiers), so attacker-controlled remote/local content cannot break out into code — no RCE. The chain stops at SSRF + RFI + LFI.
### Impact
Build-time SSRF (CWE-918) from the developer or CI host, disclosure of arbitrary local files (CWE-22), and inclusion of untrusted remote content (CWE-829), from running the generator on an attacker-controlled or attacker-influenced OpenAPI description. No code execution. Notable because Kiota is otherwise the hardened generator (it resists the code-injection class).
The relevant threat is not "change the generated output" (an attacker who ful…