### 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.
- Source published
- 24 Jul 2026 15:30:47 UTC
- Source modified
- 17 Aug 2026 15:00:08 UTC
- Observed here
- 23 Oct 2026 16:01:25 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.
CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Publisher rating · HIGH