{"id":"GHSA-p5rm-jg5c-8c77","revision":"148ab488c7cd4e74933ac2ad6ab78869","records":[{"revision":"148ab488c7cd4e74933ac2ad6ab78869","observedAt":"2026-10-23T16:01:25.029+00:00","statement":{"source":"osv","id":"GHSA-p5rm-jg5c-8c77","aliases":["CVE-2026-73851"],"title":"Microsoft Kiota: Path traversal in generated plugin manifest static_template.file reference (percent-encoding bypass)","description":"### Impact\n\nKiota generates AI plugin manifests from an OpenAPI description. When the description contains an `x-ai-capabilities` response semantics `static_template` (or the adaptive-card extension `x-ai-adaptive-card`), the `file` reference is written into the generated manifest's `response_semantics.static_template.file` and is later resolved by the AI host **relative to the plugin package**.\n\nAn attacker who controls or tampers with the OpenAPI description consumed by Kiota can supply a `file` reference that resolves **outside** the manifest package (e.g. `../../../../etc/passwd`, an absolute path, or a `file://` / `http(s)://` URI). When the generated manifest is deployed and consumed by an AI host, this can lead to inclusion or disclosure of files outside the intended package boundary (CWE-22 Path Traversal, CWE-829 Inclusion of Functionality from an Untrusted Control Sphere).\n\nA mitigation shipped in v1.32.5 (`ExtensionResponseSemanticsStaticTemplate.IsSafeFileReference`) rejected literal traversal, rooted paths, drive-qualified paths, and absolute URIs. However, that check inspected the **raw** reference string, so **percent-encoded** payloads bypassed every check and were still emitted verbatim. Examples that were incorrectly accepted as safe:\n\n| Input | Decodes to |\n|-------|-----------|\n| `%2e%2e/card.json` | `../card.json` |\n| `..%2f..%2f..%2f..%2f..%2f..%2fetc%2fpasswd` | `../../../../../../etc/passwd` |\n| `file%3A%2F%2F%2Fetc%2Fpasswd` | `file:///etc/passwd` |\n| `%2e%2e%2f%2e%2e%2f%2e%2e%2fetc%2fpasswd` | `../../../etc/passwd` |\n\nMulti-level (double) encoding such as `%252e%252e%252fcard.json` was also affected. A follow-up review found additional residual bypasses of the same validator: an embedded NUL byte (`%00`) that truncated the path and defeated the parent-directory segment check, encoding nested deeper than the decode budget (which failed open), and Unicode full-width homoglyphs (e.g. `%EF%BC%8E%EF%BC%8E` → `．．`).\n\n### Patches\n\n- The percent-encoding bypass is fixed by decoding the reference (bounded multi-pass) before validation: https://github.com/microsoft/kiota/pull/7910\n- Residual bypasses (NUL / control characters, decode-budget fail-open, Unicode homoglyphs) are fixed by failing closed on residual encoding, rejecting control characters, and NFKC-folding before validation: https://github.com/microsoft/kiota/pull/7913 (tracking issue https://github.com/microsoft/kiota/issues/7912)\n\nUsers should upgrade to the first released `Microsoft.OpenApi.Kiota` version that includes these fixes (the release following 1.33.0).\n\n### Workarounds\n\n- Only generate clients/plugins from trusted OpenAPI descriptions.\n- Review generated plugin manifests before deployment and reject any `response_semantics.static_template.file` value that is not a simple relative path within the `adaptiveCards/` package folder (no `..`, no rooted/absolute paths, no URIs, no percent-encoded separators).\n\n### References\n\n- CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')\n- CWE-829: Inclusion of Functionality from an Untrusted Control Sphere\n- Affected code: `src/Kiota.Builder/OpenApiExtensions/OpenApiAiCapabilitiesExtension.cs` (`IsSafeFileReference`) and enforcement in `src/Kiota.Builder/Plugins/PluginsGenerationService.cs`.","state":0,"publishedAt":"2026-07-24T16:14:56+00:00","modifiedAt":"2026-08-17T15:25:59.758241+00:00","affected":[{"ecosystem":"NuGet","name":"Microsoft.OpenApi.Kiota","ranges":[{"type":"ECOSYSTEM","events":[{"kind":"introduced","version":"1.30.0"},{"kind":"fixed","version":"1.34.0"}]}],"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","1.32.5","1.33.0"],"rawVersionEvidence":null},{"ecosystem":"NuGet","name":"Microsoft.OpenApi.Kiota","ranges":[{"type":"ECOSYSTEM","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"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"],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V4","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/microsoft/kiota/security/advisories/GHSA-p5rm-jg5c-8c77","https://github.com/microsoft/kiota/issues/7912","https://github.com/microsoft/kiota/pull/7910","https://github.com/microsoft/kiota/pull/7913","https://github.com/microsoft/kiota/commit/430008e9d700b3fe80f206c672415cfbd8e830e7","https://github.com/microsoft/kiota/commit/de3d18d9fe31ced4ac749728d3a2f94811f59268","https://github.com/microsoft/kiota","https://github.com/microsoft/kiota/releases/tag/v1.34.0"],"sourceUrl":"https://github.com/advisories/GHSA-p5rm-jg5c-8c77","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-p5rm-jg5c-8c77","identifiers":["GHSA-p5rm-jg5c-8c77","CVE-2026-73851"]},"retained":false,"historicalAffected":[]}],"coverage":[]}