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CVE-2026-73851

Path Traversal in Microsoft.OpenApi.Kiota (CVE-2026-73851)

Summary

Path traversal in Microsoft.OpenApi.Kiota (CVE-2026-73851). Risk of unauthorized operations or information disclosure. Exploitable via static_template. Mitigation: upgrade to 1.29.1 or later.

Original description

The description as published by the source.

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
…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-73851 has been found in Microsoft.OpenApi.Kiota.
Attackers can target a specific entry point like static_template over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade Microsoft.OpenApi.Kiota to 1.29.1 or later.
If unsure, ask your IT team or search "Microsoft.OpenApi.Kiota CVE-2026-73851" on the vendor's site.

CVE-2026-73851 (Microsoft.OpenApi.Kiota) — CWE-22
Attack surface: static_template / file / response_semantics.static_template.file / Microsoft.OpenApi.Kiota
Patched: 1.29.1 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Path traversal (CWE-22) exists in Microsoft.OpenApi.Kiota. Attackers reach the vulnerable code path via static_template.

📍 Affected scope

Check the vendor advisory for the affected versions of Microsoft.OpenApi.Kiota. Attack surface: static_template / file / response_semantics.static_template.file / Microsoft.OpenApi.Kiota.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 1.29.1.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Microsoft.OpenApi.Kiota' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'Microsoft.OpenApi.Kiota' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Microsoft.OpenApi.Kiota を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade Microsoft.OpenApi.Kiota to 1.29.1

    ステージング環境で 1.29.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

nuget Microsoft.OpenApi.Kiota
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.29.1"}]}]

References

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