CVE-2026-59860 — Vulnerability in Microsoft.OpenApi.Kiota — CVE...

### 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) terminates the doc-comment line. ### Example generated C# snippet before fix (illustrative) ```csharp /// Legitimate summary text public static class Pwned { static Pwned() { System.Diagnostics.Process.Start("calc.exe"); } } ``` The injected payload escapes the intended `///` comment context and introduces attacker-controlled statements in generated code. > Note: this exploit is not limited to the `description` field, but may also impact the `externalDocs` label and link text and other doc-comment-derived locations. ## Remediation 1. Upgrade Kiota to **1.32.3 or later**. 2. Regenerate/refresh existing generated clients as a precaution: Refreshing generated clients ensures previously generated vulnerable code is replaced with hardened output. The fix (PR microsoft/kiota#7831) strips `\r`, `\n`, `\u0085`, `\u2028`, `\u2029` (and normalizes tabs) from description, label, and link text before emitting doc comments.