GHSA-4vv7-jj25-4gh6 Microsoft Kiota: Arbitrary file write + code-injection via x-ms-kiota-info clientClassName and clientNamespaceName

• NuGet Microsoft.OpenApi.Kiota: >= 1.30.0, < 1.32.5 → fixed in 1.32.5 • NuGet Microsoft.OpenApi.Kiota.Builder: >= 1.30.0, < 1.32.5 → fixed in 1.32.5 • NuGet Microsoft.OpenApi.Kiota: < 1.29.1 → fixed in 1.29.1 • NuGet Microsoft.OpenApi.Kiota.Builder: < 1.29.1 → fixed in 1.29.1

Summary Microsoft Kiota emitted the `x-ms-kiota-info` extension's `clientClassName` or `clientNamespaceName` value raw, with no identifier or path sanitization, as both the generated client's class/namespace name and part of the generated output path. When `kiota generate` is run without `-c/--class-name` — the zero-config workflow that `x-ms-kiota-info` is explicitly designed for (the API provider supplies the names in the description so consumers don't have to) — an attacker who controls or tampers with the OpenAPI description could therefore: • (CWE-22) write the generated source file to a path outside the `-o` output directory — e.g. `clientClassName: "/var/www/html/shell"`; and • (CWE-94) inject arbitrary text into the generated class/namespace declaration, corrupting the generated client. Confirmed on Kiota 1.32.4 (the self-contained `linux-x64` release binary), i.e. after the earlier writer-sink hardening — that fix escaped property/enum/default/serialization sinks but never sanitized the provider-supplied `clientClassName` / `clientNamespaceName`. Details `clientClassName` reached two unsanitized sinks (observed in the generated C#; the same raw emission occurred for Java, Go, TypeScript, Python, and PHP): ``` output FILENAME (CWE-22): clientClassName flows into the file path clientClassName: "/abs/path/PWNED" -> /abs/path/PWNED.cs (written outside -o) class declaration (CWE-94): clientClassName flows verbatim into the type declaration clientClassName: 'Pwn { } public class INJECTED { } public partial class RealClient' -> public partial class Pwn { } public class INJECTED { } public partial class RealClient : ... { } ``` `clientNamespaceName` reached the analogous namespace/path sinks. Impact A developer or CI host generating a client from an attacker-controlled or compromised OpenAPI description (without `-c`) could create/overwrite a generated source file at an attacker-influenced path and emit attacker-controlled text into the generated client. This does not reach clean remote code execution: because `clientClassName` is reused verbatim at multiple sites (the class name and the constructor name), injected code cannot be made to compile — it breaks the build. So the code-injection vector is a generation/build-corruption (integrity/DoS), and the high-severity primitive is the file write. CWE-22 / CWE-94. Patches Fixed in 1.29.1 and 1.32.5 (https://github.com/microsoft/kiota/pull/7884). `clientClassName` and `clientNamespaceName` sourced from `x-ms-kiota-info` are now sanitized before use: `GenerationConfiguration.SanitizeClientClassName` strips any character outside `[A-Za-z0-9_]` and any invalid leading character (falling back to `ApiClient`), and `SanitizeClientNamespaceName` restricts to `[A-Za-z0-9._-]`, collapses consecutive dots, strips invalid leading characters (falling back to `ApiSdk`). This removes path separators, drive/colon, `..`, quotes, and braces, so the values can no longer influence the output path or inject into the declaration. Remediation Upgrade to Kiota 1.29.1, 1.32.5, or later and regenerate affected clients.