What is CVE-2026-59864?

### Summary `kiota plugin add` / `kiota plugin generate` (with `-t APIPlugin`) emits an attacker-controlled `static_template.file` path from the AI-plugin extensions (`x-ai-adaptive-card`, `x-ai-capabilities`) **verbatim**, with no path validation, into the generated Microsoft 365 Copilot / Teams plugin manifest (` -apiplugin.json`). An attacker-controlled or compromised OpenAPI description can therefore embed a `../` / absolute path into the manifest's `response_semantics.static_template.file`, yielding a **path traversal (CWE-22)** / out-of-package file inclusion (CWE-829) that is reso

How severe is CVE-2026-59864?

No CVSS score has been assigned to CVE-2026-59864 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-59864?

CVE-2026-59864 affects the following packages: Microsoft.OpenApi.Kiota (NuGet), Microsoft.OpenApi.Kiota.Builder (NuGet), Microsoft.OpenApi.Kiota (NuGet), Microsoft.OpenApi.Kiota.Builder (NuGet). Ecosystems affected: NuGet.

How do I fix CVE-2026-59864?

Update Microsoft.OpenApi.Kiota to 1.32.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-59864 is resolved across your whole dependency graph.

How do I detect CVE-2026-59864 in my NuGet dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.OpenApi.Kiota, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-59864 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2026-59864 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-59864 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-59864?

CVE-2026-59864 has an EPSS (Exploit Prediction Scoring System) score of 1.3%, placing it in the 71th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-59864?

CVE-2026-59864 is classified as Path Traversal (CWE-22), CWE-829 (CWE-829). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-59864 published, and has it been updated?

CVE-2026-59864 was published on July 16, 2026 and was last updated on October 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET NuGet

Not in CISA KEV

CVE-2026-59864 — Microsoft.OpenApi.Kiota

Fix: microsoft/kiota@9a18599

CVE-2026-59864 is a Path Traversal vulnerability in Microsoft.OpenApi.Kiota. A fix is available for Microsoft.OpenApi.Kiota — see the affected versions and patch details below.

Kiota: Path/URL injection into generated Copilot plugin manifest via x-ai-* extensions

Also known asGHSA-4jwf-m4wg-8p66

Published

Jul 16, 2026

Updated

Oct 7, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

None indexed

Exploitation data as of Oct 15, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-59864.

EPSS Exploitation Probability

via FIRST.org ↗

1.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs71th percentile — riskier than 71% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

4 pkgs affected

.NETMicrosoft.OpenApi.Kiota.NETMicrosoft.OpenApi.Kiota.Builder.NETMicrosoft.OpenApi.Kiota.NETMicrosoft.OpenApi.Kiota.Builder

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

Summary

kiota plugin add / kiota plugin generate (with -t APIPlugin) emits an attacker-controlled static_template.file path from the AI-plugin extensions (x-ai-adaptive-card, x-ai-capabilities) verbatim, with no path validation, into the generated Microsoft 365 Copilot / Teams plugin manifest (<name>-apiplugin.json). An attacker-controlled or compromised OpenAPI description can therefore embed a ../ / absolute path into the manifest's response_semantics.static_template.file, yielding a path traversal (CWE-22) / out-of-package file inclusion (CWE-829) that is resolved by the AI host when the generated plugin is deployed.

Confirmed on Kiota 1.32.4 (KIOTA_CONFIG_PREVIEW=true, the self-contained linux-x64 release binary).

Details

Both extension paths write the static_template.file reference straight into the manifest without sanitization — PluginsGenerationService.GetResponseSemanticsFromAdaptiveCardExtension mints static_template = {"file": <File>}, and the x-ai-capabilities path copies the static_template object through:

# spec                                                  -> generated manifest (functions[].capabilities.response_semantics)
x-ai-adaptive-card: {title: T, data_path: $.x,
   file: "../../../../../../etc/passwd"}                -> static_template.file = "../../../../../../etc/passwd"   (CWE-22)
x-ai-capabilities.response_semantics.static_template:
   {file: "../../../../../../etc/passwd"}               -> static_template.file = "../../../../../../etc/passwd"   (CWE-22)

(x-ai-adaptive-card.file only reaches the manifest when title is set, so GetResponseSemanticsFromAdaptiveCardExtension fires; otherwise kiota writes its own template card instead.)

Impact

This is not local code execution on the build host. The injected path is written into the generated plugin manifest and realized downstream, when the plugin is packaged and sideloaded / deployed to an AI host (Microsoft 365 Copilot / Teams) that resolves static_template.file relative to the plugin package (out-of-package file reference via ../). Kiota is the propagation point: it fails to reject ../ and absolute paths in this provider-supplied field before writing it into the manifest.

Patches

Fixed in 1.29.1 and 1.32.5 (https://github.com/microsoft/kiota/pull/7892). static_template.file from both x-ai-adaptive-card and x-ai-capabilities is validated as a relative path confined to the plugin output package: absolute URIs, rooted/UNC paths, Windows drive paths, and .. traversal segments are rejected, and unsafe references are dropped with a warning. Regression tests cover .., absolute paths, and URI values.

Remediation

Upgrade to Kiota 1.29.1, 1.32.5 or later and regenerate affected plugins.

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`Microsoft.OpenApi.Kiota`	≥ 1.30.0&&< 1.32.5	1.32.5`dotnet add package Microsoft.OpenApi.Kiota --version 1.32.5`
.NETNuGet	`Microsoft.OpenApi.Kiota.Builder`	≥ 1.30.0&&< 1.32.5	1.32.5`dotnet add package Microsoft.OpenApi.Kiota.Builder --version 1.32.5`
.NETNuGet	`Microsoft.OpenApi.Kiota`	all versions	1.29.1`dotnet add package Microsoft.OpenApi.Kiota --version 1.29.1`
.NETNuGet	`Microsoft.OpenApi.Kiota.Builder`	all versions	1.29.1`dotnet add package Microsoft.OpenApi.Kiota.Builder --version 1.29.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.OpenApi.Kiota, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.OpenApi.Kiota to 1.32.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-59864 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

### Summary `kiota plugin add` / `kiota plugin generate` (with `-t APIPlugin`) emits an attacker-controlled `static_template.file` path from the AI-plugin extensions (`x-ai-adaptive-card`, `x-ai-capabilities`) **verbatim**, with no path validation, into the generated Microsoft 365 Copilot / Teams plugin manifest (`<name>-apiplugin.json`). An attacker-controlled or compromised OpenAPI description can therefore embed a `../` / absolute path into the manifest's `response_semantics.static_template.file`, yielding a **path traversal (CWE-22)** / out-of-package file inclusion (CWE-829) that is reso

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