{"id":"CVE-2026-59866","aliases":["EUVD-2026-44936","GHSA-4vv7-jj25-4gh6"],"status":"published","title":"Kiota: Arbitrary file write + code-injection via x-ms-kiota-info clientClassName and clientNamespaceName","description":"Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.5, Kiota emitted x-ms-kiota-info clientClassName and clientNamespaceName values without identifier or path sanitization as both generated client class or namespace names and generated output path components when `kiota generate` ran without -c/--class-name, allowing an attacker-controlled or compromised OpenAPI description to write generated source outside the -o output directory and inject arbitrary text into generated class or namespace declarations. This issue is fixed in version 1.29.1 and 1.32.5 by GenerationConfiguration.SanitizeClientClassName and SanitizeClientNamespaceName.","severity":{"version":"4.0","score":9.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.01413,"percentile":0.72943,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-22","CWE-94"],"published":"2026-07-16T14:46:50Z","modified":"2026-11-07T02:48:39Z","fixes":[{"ecosystem":"NuGet","package":"Microsoft.OpenApi.Kiota","fixed_in":["1.32.5","1.29.1"],"sources":["ghsa","osv"]},{"ecosystem":"NuGet","package":"Microsoft.OpenApi.Kiota.Builder","fixed_in":["1.32.5","1.29.1"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"NuGet","package":"Microsoft.OpenApi.Kiota","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.30.0"},{"fixed":"1.32.5"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Microsoft.OpenApi.Kiota.Builder","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.30.0"},{"fixed":"1.32.5"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Microsoft.OpenApi.Kiota","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.29.1"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Microsoft.OpenApi.Kiota.Builder","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.29.1"}]}]},{"source":"osv","ecosystem":"NuGet","package":"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"]},{"source":"osv","ecosystem":"NuGet","package":"Microsoft.OpenApi.Kiota.Builder","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.30.0"},{"fixed":"1.32.5"}]}]},{"source":"osv","ecosystem":"NuGet","package":"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"]},{"source":"osv","ecosystem":"NuGet","package":"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"]}],"products":[{"vendor":"microsoft","product":"kiota"}],"references":[{"url":"https://github.com/microsoft/kiota/security/advisories/GHSA-4vv7-jj25-4gh6","tags":["x_refsource_CONFIRM","advisory","web"]},{"url":"https://github.com/microsoft/kiota/pull/7884","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/kiota/commit/dc812dbbf88ef7edf53a890d36b2f9d1460e947d","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/kiota/releases/tag/v1.32.5","tags":["x_refsource_MISC","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59866","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-4vv7-jj25-4gh6"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59866.json","tags":["advisory"]},{"url":"https://github.com/microsoft/kiota","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-59866","title":"Kiota: Arbitrary file write + code-injection via x-ms-kiota-info clientClassName and clientNamespaceName","description":"Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.5, Kiota emitted x-ms-kiota-info clientClassName and clientNamespaceName values without identifier or path sanitization as both generated client class or namespace names and generated output path components when `kiota generate` ran without -c/--class-name, allowing an attacker-controlled or compromised OpenAPI description to write generated source outside the -o output directory and inject arbitrary text into generated class or namespace declarations. This issue is fixed in version 1.29.1 and 1.32.5 by GenerationConfiguration.SanitizeClientClassName and SanitizeClientNamespaceName.","status":"published","published":"2026-07-16T14:46:50.738Z","modified":"2026-08-17T15:03:20.823Z","cvss":[{"version":"4.0","score":9.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","level":"critical","assessor":"cna"}],"cwes":["CWE-22","CWE-94"],"updated_at":"2026-11-02T14:19:58.560602Z"}],"euvd":[{"id":"EUVD-2026-44936","description":"Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.5, Kiota emitted x-ms-kiota-info clientClassName and clientNamespaceName values without identifier or path sanitization as both generated client class or namespace names and generated output path components when `kiota generate` ran without -c/--class-name, allowing an attacker-controlled or compromised OpenAPI description to write generated source outside the -o output directory and inject arbitrary text into generated class or namespace declarations. This issue is fixed in version 1.29.1 and 1.32.5 by GenerationConfiguration.SanitizeClientClassName and SanitizeClientNamespaceName.","status":"published","published":"2026-07-16T14:46:50Z","modified":"2026-08-17T15:03:20Z","cvss":[{"version":"4.0","score":9.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","level":"critical"}],"updated_at":"2026-11-02T18:01:49.335011Z"}],"ghsa":[{"id":"GHSA-4vv7-jj25-4gh6","title":"Microsoft Kiota: Arbitrary file write + code-injection via x-ms-kiota-info clientClassName and clientNamespaceName","description":"### 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.","status":"published","published":"2026-07-24T16:12:14Z","modified":"2026-08-17T14:55:50Z","cvss":[{"version":"4.0","score":7,"vector":"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","level":"high"}],"cwes":["CWE-22","CWE-94"],"updated_at":"2026-11-02T14:41:01.23108Z"}],"nvd":[{"id":"CVE-2026-59866","description":"Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.5, Kiota emitted x-ms-kiota-info clientClassName and clientNamespaceName values without identifier or path sanitization as both generated client class or namespace names and generated output path components when `kiota generate` ran without -c/--class-name, allowing an attacker-controlled or compromised OpenAPI description to write generated source outside the -o output directory and inject arbitrary text into generated class or namespace declarations. This issue is fixed in version 1.29.1 and 1.32.5 by GenerationConfiguration.SanitizeClientClassName and SanitizeClientNamespaceName.","status":"published","published":"2026-07-16T16:19:15.493Z","modified":"2026-10-24T20:10:00.137Z","cvss":[{"version":"4.0","score":9.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical","assessor":"secondary"}],"cwes":["CWE-22","CWE-94"],"updated_at":"2026-11-02T14:12:30.250437Z"}],"osv":[{"id":"CVE-2026-59866","title":"Kiota: Arbitrary file write + code-injection via x-ms-kiota-info clientClassName and clientNamespaceName","description":"Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.5, Kiota emitted x-ms-kiota-info clientClassName and clientNamespaceName values without identifier or path sanitization as both generated client class or namespace names and generated output path components when `kiota generate` ran without -c/--class-name, allowing an attacker-controlled or compromised OpenAPI description to write generated source outside the -o output directory and inject arbitrary text into generated class or namespace declarations. This issue is fixed in version 1.29.1 and 1.32.5 by GenerationConfiguration.SanitizeClientClassName and SanitizeClientNamespaceName.","status":"published","published":"2026-07-16T14:46:50.738Z","modified":"2026-11-07T02:48:39.661982981Z","cvss":[{"version":"4.0","score":9.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","level":"critical"}],"cwes":["CWE-22","CWE-94"],"updated_at":"2026-11-07T03:08:08.148548Z"},{"id":"GHSA-4vv7-jj25-4gh6","title":"Microsoft Kiota: Arbitrary file write + code-injection via x-ms-kiota-info clientClassName and clientNamespaceName","description":"### 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.","status":"published","published":"2026-07-24T16:12:14Z","modified":"2026-08-17T15:00:08.105646988Z","cvss":[{"version":"4.0","score":7,"vector":"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","level":"high"}],"cwes":["CWE-22","CWE-94"],"updated_at":"2026-11-02T15:46:37.528068Z"}]}}