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High, CVSS 7.1

Microsoft Kiota: Generation-time SSRF + remote/local file inclusion via unrestricted $ref

CVE-2026-59867GHSA-rg4h-fpcp-2qm8

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (microsoft.openapi.kiota 1.32.5, 1.29.1; microsoft.openapi.kiota.builder 1.32.5, 1.29.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
EPSS
  • CVE-2026-59867: 2.39% estimated exploitation activity in the next 30 days; percentile 84.00 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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 REMOTEKIOTAPROP 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.…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-rg4h-fpcp-2qm8

Agent brief

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# Patch Next advisory brief: CVE-2026-59867

Advisory: Microsoft Kiota: Generation-time SSRF + remote/local file inclusion via unrestricted $ref
IDs: CVE-2026-59867, GHSA-rg4h-fpcp-2qm8
Record: https://patchnext.com/advisories/cve-2026-59867 (revision 1, source checked 26 Oct 2026, 17:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: microsoft.openapi.kiota 1.32.5, 1.29.1; microsoft.openapi.kiota.builder 1.32.5, 1.29.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet microsoft.openapi.kiota: affected >= 1.30.0, < 1.32.5; < 1.29.1; fixed in 1.29.1, 1.32.5
- NuGet microsoft.openapi.kiota.builder: affected >= 1.30.0, < 1.32.5; < 1.29.1; fixed in 1.29.1, 1.32.5

## Suggested inspection (read-only)
- NuGet microsoft.openapi.kiota: check the installed version with your package manager.
- NuGet microsoft.openapi.kiota.builder: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on microsoft.openapi.kiota, microsoft.openapi.kiota.builder.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-rg4h-fpcp-2qm8 (GitHub-reviewed advisory GHSA-rg4h-fpcp-2qm8 lists affected ranges: NuGet microsoft.openapi.kiota >=1.30.0 =0 =1.30.0 =0 <1.29.1)

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