{"id":"GHSA-4vv7-jj25-4gh6","summary":"Microsoft Kiota: Arbitrary file write + code-injection via x-ms-kiota-info clientClassName and clientNamespaceName","details":"### Summary\n\nMicrosoft Kiota emitted the `x-ms-kiota-info` extension's `clientClassName` or `clientNamespaceName` value\n**raw**, with no identifier or path sanitization, as **both** the generated client's class/namespace name\n**and** part of the generated output path. When `kiota generate` is run **without `-c/--class-name`** — the\nzero-config workflow that `x-ms-kiota-info` is explicitly designed for (the API provider supplies the names in\nthe description so consumers don't have to) — an attacker who controls or tampers with the OpenAPI description\ncould therefore:\n\n- **(CWE-22) write the generated source file to a path outside the `-o` output directory** — e.g.\n  `clientClassName: \"/var/www/html/shell\"`; and\n- **(CWE-94) inject arbitrary text into the generated class/namespace declaration**, corrupting the generated\n  client.\n\nConfirmed on Kiota **1.32.4** (the self-contained `linux-x64` release binary), i.e. **after** the earlier\nwriter-sink hardening — that fix escaped property/enum/default/serialization sinks but never sanitized the\nprovider-supplied `clientClassName` / `clientNamespaceName`.\n\n### Details\n\n`clientClassName` reached two unsanitized sinks (observed in the generated C#; the same raw emission occurred\nfor Java, Go, TypeScript, Python, and PHP):\n\n```\n# output FILENAME (CWE-22): clientClassName flows into the file path\nclientClassName: \"/abs/path/PWNED\"   -\u003e   /abs/path/PWNED.cs   (written outside -o)\n\n# class declaration (CWE-94): clientClassName flows verbatim into the type declaration\nclientClassName: 'Pwn { } public class INJECTED { } public partial class RealClient'\n   -\u003e  public partial class Pwn { } public class INJECTED { } public partial class RealClient : ... { }\n```\n\n`clientNamespaceName` reached the analogous namespace/path sinks.\n\n### Impact\n\nA developer or CI host generating a client from an attacker-controlled or compromised OpenAPI description\n(without `-c`) could create/overwrite a generated source file at an attacker-influenced path and emit\nattacker-controlled text into the generated client.\n\nThis does **not** reach clean remote code execution: because `clientClassName` is reused verbatim at multiple\nsites (the class name **and** the constructor name), injected code cannot be made to compile — it breaks the\nbuild. So the code-injection vector is a generation/build-corruption (integrity/DoS), and the high-severity\nprimitive is the file write. CWE-22 / CWE-94.\n\n### Patches\n\nFixed in **1.29.1 and 1.32.5** (https://github.com/microsoft/kiota/pull/7884). `clientClassName` and\n`clientNamespaceName` sourced from `x-ms-kiota-info` are now sanitized before use:\n`GenerationConfiguration.SanitizeClientClassName` strips any character outside `[A-Za-z0-9_]` and any invalid\nleading character (falling back to `ApiClient`), and `SanitizeClientNamespaceName` restricts to\n`[A-Za-z0-9._-]`, collapses consecutive dots, strips invalid leading characters (falling back to `ApiSdk`).\nThis removes path separators, drive/colon, `..`, quotes, and braces, so the values can no longer influence\nthe output path or inject into the declaration.\n\n### Remediation\n\nUpgrade to Kiota **1.29.1, 1.32.5,** or later and regenerate affected clients.","aliases":["CVE-2026-59866"],"modified":"2026-08-17T15:00:08.105646988Z","published":"2026-07-24T16:12:14Z","database_specific":{"cwe_ids":["CWE-22","CWE-94"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-07-24T16:12:14Z","nvd_published_at":"2026-07-16T16:19:15Z"},"references":[{"type":"WEB","url":"https://github.com/microsoft/kiota/security/advisories/GHSA-4vv7-jj25-4gh6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59866"},{"type":"WEB","url":"https://github.com/microsoft/kiota/pull/7884"},{"type":"WEB","url":"https://github.com/microsoft/kiota/commit/dc812dbbf88ef7edf53a890d36b2f9d1460e947d"},{"type":"PACKAGE","url":"https://github.com/microsoft/kiota"},{"type":"WEB","url":"https://github.com/microsoft/kiota/releases/tag/v1.32.5"}],"affected":[{"package":{"name":"Microsoft.OpenApi.Kiota","ecosystem":"NuGet","purl":"pkg:nuget/Microsoft.OpenApi.Kiota"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.30.0"},{"fixed":"1.32.5"}]}],"versions":["1.30.0","1.31.0","1.31.1","1.32.0","1.32.1","1.32.2","1.32.3","1.32.4"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-4vv7-jj25-4gh6/GHSA-4vv7-jj25-4gh6.json"}},{"package":{"name":"Microsoft.OpenApi.Kiota.Builder","ecosystem":"NuGet","purl":"pkg:nuget/Microsoft.OpenApi.Kiota.Builder"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.30.0"},{"fixed":"1.32.5"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-4vv7-jj25-4gh6/GHSA-4vv7-jj25-4gh6.json"}},{"package":{"name":"Microsoft.OpenApi.Kiota","ecosystem":"NuGet","purl":"pkg:nuget/Microsoft.OpenApi.Kiota"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.29.1"}]}],"versions":["0.1.0-preview","0.1.1-preview","0.1.2-preview","0.1.3-preview","0.10.0-preview","0.11.0-preview","0.11.1-preview","0.2.0-preview","0.2.1-preview","0.3.0-preview","0.4.0-preview","0.5.0-preview","0.5.1-preview","0.6.0-preview","0.7.1-preview","0.8.3-preview","0.9.0-preview","1.0.0","1.0.1","1.1.0","1.1.1","1.1.2","1.1.3","1.10.0","1.10.1","1.11.0","1.11.1","1.12.0","1.13.0","1.14.0","1.15.0","1.16.0","1.17.0","1.18.0","1.19.0","1.19.1","1.2.0","1.2.1","1.20.0","1.21.0","1.22.0","1.22.1","1.22.2","1.22.3","1.23.0","1.24.0","1.24.1","1.24.2","1.24.3","1.25.1","1.26.0","1.26.1","1.27.0","1.28.0","1.29.0","1.3.0","1.4.0","1.5.0","1.5.1","1.6.1","1.7.0","1.8.0","1.8.1","1.8.2","1.9.0","1.9.1"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-4vv7-jj25-4gh6/GHSA-4vv7-jj25-4gh6.json"}},{"package":{"name":"Microsoft.OpenApi.Kiota.Builder","ecosystem":"NuGet","purl":"pkg:nuget/Microsoft.OpenApi.Kiota.Builder"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.29.1"}]}],"versions":["0.2.0-preview","0.3.0-preview","0.4.0-preview","0.5.0-preview","0.5.1-preview","0.6.0-preview","0.7.1-preview","1.0.0","1.0.1","1.1.0","1.1.1","1.1.2","1.1.3","1.10.0","1.10.1","1.11.0","1.11.1","1.12.0","1.13.0","1.14.0","1.15.0","1.16.0","1.17.0","1.18.0","1.19.0","1.19.1","1.2.0","1.2.1","1.20.0","1.21.0","1.22.0","1.22.1","1.22.2","1.22.3","1.23.0","1.3.0","1.4.0","1.5.0","1.5.1","1.6.1","1.7.0","1.8.0","1.8.1","1.8.2","1.9.0","1.9.1"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-4vv7-jj25-4gh6/GHSA-4vv7-jj25-4gh6.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N"}]}