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CVE-2026-59867 high CVSS 7.1

Path Traversal in Microsoft.OpenApi.Kiota (CVE-2026-59867)

Summary

Path traversal in Microsoft.OpenApi.Kiota (CVE-2026-59867). Confidential information can be exposed externally. Exploitable via REMOTE_KIOTA_PROP. Mitigation: upgrade to 1.29.1 or later.

Original description

The description as published by the source.

Summary

Microsoft Kiota resolved OpenAPI $refs by fetching remote http(s) URLs and reading local files
(including absolute / out-of-tree paths), inlining the referenced schema into the generated client.
Running kiota generate on a spec whose $ref pointed at an attacker/internal URL or an arbitrary
local file yielded SSRF, remote file inclusion, and local file inclusion. Verified on 1.32.3 / 1.32.4.

Details

  • $ref: http://attacker/internal-evil.json#/... → build host fetches the URL (SSRF) and inlines the
    remote schema (RFI); confirmed property REMOTE_KIOTA_PROP in the generated client.
  • $ref: /abs/path.json#/... or ../../secret.json#/... → Kiota reads the out-of-tree local file and
    inlines its schema (LFI); confirmed Leaked schema in the generated client. Resolution is transitive
    across nesting levels.

Kiota escapes its output sinks (comments/strings/identifiers), so attacker-controlled remote/local
content cannot break out into code — no RCE. The chain stops at SSRF + RFI + LFI.

Impact

Build-time SSRF (CWE-918) from the developer or CI host, disclosure of arbitrary local files (CWE-22), and
inclusion of untrusted remote content (CWE-829), from running the generator on an attacker-controlled or
attacker-influenced OpenAPI description. No code execution. Notable because Kiota is otherwise the hardened
generator (it resists the code-injection class).

The relevant threat is not "change the generated output" (an attacker who full…

Source: NIST National Vulnerability Database 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-2026-59867 has been found in Microsoft.OpenApi.Kiota.
Attackers can target a specific entry point like REMOTE_KIOTA_PROP over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.1/10.
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-2026-59867" on the vendor's site.

CVE-2026-59867 (Microsoft.OpenApi.Kiota) — CWE-22 / CVSS v3 7.1
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: REMOTE_KIOTA_PROP / Leaked / AllowedExternalOriginsStreamLoader
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 REMOTE_KIOTA_PROP without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of Microsoft.OpenApi.Kiota. Attack surface: REMOTE_KIOTA_PROP / Leaked / AllowedExternalOriginsStreamLoader.

🔥 Severity

Severity: High (CVSS 7.1/10). Confidential information can be exposed externally.

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

References

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