Kiota: Path traversal in generated plugin manifest static_template.file reference (percent-encoding bypass)

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.34.0, an 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. This vulnerability is fixed in 1.29.1 and 1.34.0.

Source published

17 Aug 2026 15:11:39 UTC

Source modified

17 Aug 2026 15:26:40 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 6.1 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

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.34.0, an 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. This vulnerability is fixed in 1.29.1 and 1.34.0.

Source published

17 Aug 2026 15:16:57 UTC

Source modified

24 Oct 2026 15:10:00 UTC

Observed here

25 Oct 2026 15:19:09 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 6.1 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/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

### Impact Kiota 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**. An 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). A 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: | Input | Decodes to | |-------|-----------| | `%2e%2e/card.json` | `../card.json` | | `..%2f..%2f..%2f..%2f..%2f..%2fetc%2fpasswd` | `../../../../../../etc/passwd` | | `file%3A%2F%2F%2Fetc%2Fpasswd` | `file:///etc/passwd` | | `%2e%2e%2f%2e%2e%2f%2e%2e%2fetc%2fpasswd` | `../../../etc/passwd` | Multi-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` → `．．`). ### Patches - The percent-encoding bypass is fixed by decoding the reference (bounded multi-pass) before validation: https://github.com/microsoft/kiota/pull/7910 - 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) Users should upgrade to the first released `Microsoft.OpenApi.Kiota` version that includes these fixes (the release following 1.33.0). ### Workarounds - Only generate clients/plugins from trusted OpenAPI descriptions. - 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). ### References - CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') - CWE-829: Inclusion of Functionality from an Untrusted Control Sphere - Affected code: `src/Kiota.Builder/OpenApiExtensions/OpenApiAiCapabilitiesExtension.cs` (`IsSafeFileReference`) and enforcement in `src/Kiota.Builder/Plugins/PluginsGenerationService.cs`.

Source published

24 Jul 2026 16:14:56 UTC

Source modified

17 Aug 2026 15:25:59 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:A/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N

Publisher rating · MODERATE