EUVD-2026-354313

fkie_cve-2026-59860

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.3, Kiota is affected by a code-generation injection vulnerability in the C# XML documentation-comment sink (the description, externalDocs label, and externalDocs link fields emitted as /// … comments). When text from an OpenAPI description is written into single-line XML doc comments without stripping newline and Unicode line-terminator characters, an attacker can break out of the /// comment line and inject additional code into generated C# clients. This issue is fixed in version 1.29.1 and 1.32.3.

GHSA-3hrf-2gc2-mx32 — Microsoft Kiota: XML Doc-Comment Newline Breakout Code Injection

Affected: NuGet: Microsoft.OpenApi.Kiota, NuGet: Microsoft.OpenApi.Kiota.Builder

### Summary

Kiota versions **prior to 1.32.3 and 1.29.1** are affected by a code-generation injection vulnerability in the C# XML documentation-comment sink (the `description`, `externalDocs` label, and `externalDocs` link fields emitted as `/// …` comments).

When text from an OpenAPI description is written into single-line XML doc comments without stripping newline and Unicode line-terminator characters, an attacker can break out of the `///` comment line and inject additional code into generated C# clients.

## Impact and Preconditions

This issue is only practically exploitable when:

1. the OpenAPI description used for generation is from an **untrusted source**, or 2. a normally trusted OpenAPI description has been **compromised/tampered with**.

The injected code is compiled (and may execute) when the developer or CI **builds** the generated client. If you only generate from trusted, integrity-protected API descriptions, risk is significantly reduced.

## Affected Versions

- **Affected:** all versions **< 1.29.1**, **>= 1.30.0, < 1.32.3** - **Fixed: 1.29.1, 1.32.3,** and later

## Illustrative Exploit Example

### Example OpenAPI fragment (malicious description)

```yaml openapi: 3.0.1 info: title: Exploit Demo version: 1.0.0 description: |- Legitimate summary text public static class Pwned { static Pwned() { System.Diagnostics.Process.Start("calc.exe"); } } ```

The newline inside `description` (also exploitable via `\r`, U+0085, U+2028, U+2029) term…

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EUVD-2026-354313

fkie_cve-2026-59860

GHSA-3hrf-2gc2-mx32 — Microsoft Kiota: XML Doc-Comment Newline Breakout Code Injection