CVE-2026-59867: Microsoft Kiota Generation-time SSRF + Remote/local File Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rg4h-fpcp-2qm8",
  "modified" : "2026-08-17T14:56:30Z",
  "published" : "2026-07-24T16:10:17Z",
  "aliases" : [ "CVE-2026-59867" ],
  "summary" : "Microsoft Kiota: Generation-time SSRF + remote/local file inclusion via unrestricted $ref",
  "details" : "## Summary\n\nMicrosoft Kiota resolved OpenAPI `$ref`s by fetching remote `http(s)` URLs and reading local files\n(including absolute / out-of-tree paths), inlining the referenced schema into the generated client.\nRunning `kiota generate` on a spec whose `$ref` pointed at an attacker/internal URL or an arbitrary\nlocal file yielded SSRF, remote file inclusion, and local file inclusion. Verified on **1.32.3 / 1.32.4**.\n\n### Details\n\n- `$ref: http://attacker/internal-evil.json#/...` → build host fetches the URL (SSRF) and inlines the\n  remote schema (RFI); confirmed property `REMOTE_KIOTA_PROP` in the generated client.\n- `$ref: /abs/path.json#/...` or `../../secret.json#/...` → Kiota reads the out-of-tree local file and\n  inlines its schema (LFI); confirmed `Leaked` schema in the generated client. Resolution is transitive\n  across nesting levels.\n\nKiota **escapes** its output sinks (comments/strings/identifiers), so attacker-controlled remote/local\ncontent cannot break out into code — no RCE. The chain stops at SSRF + RFI + LFI.\n\n### Impact\n\nBuild-time SSRF (CWE-918) from the developer or CI host, disclosure of arbitrary local files (CWE-22), and\ninclusion of untrusted remote content (CWE-829), from running the generator on an attacker-controlled or\nattacker-influenced OpenAPI description. No code execution. Notable because Kiota is otherwise the hardened\ngenerator (it resists the code-injection class).\n\nThe relevant threat is not \"change the generated output\" (an attacker who fully controls the description can\nalready do that) but the **side effects on the build host**: outbound requests from inside the CI network\n(cloud metadata, internal-only services) and reads of local files the attacker never possessed, whose contents\nare then inlined into the generated — and typically committed/published — client. It also bypasses controls\nthat review the description document but not externally-referenced content.\n\n### Patches\n\nFixed in **1.29.1 and 1.32.5** (https://github.com/microsoft/kiota/pull/7888). External reference resolution is now\n**default-deny**: a new `AllowedExternalOriginsStreamLoader` refuses to load any external `$ref` — remote\n`http(s)` URLs and local file paths alike — unless its origin/path is explicitly allow-listed. A new\n`--allowed-external-origins` parameter (added to the commands that load OpenAPI descriptions) opts specific\norigins back in, accepting `*`, full URIs, URI patterns, full paths, relative paths, or path patterns\n(wildcards supported). With no allow-list entries, external references are not loaded at all.\n\n### Remediation\n\nUpgrade to Kiota **1.29.1, 1.32.5,** or later. External references now require explicit opt-in via\n`--allowed-external-origins`; add only trusted origins/paths.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.30.0"
      }, {
        "fixed" : "1.32.5"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota.Builder"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.30.0"
      }, {
        "fixed" : "1.32.5"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.29.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota.Builder"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.29.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/security/advisories/GHSA-rg4h-fpcp-2qm8"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-59867"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/pull/7888"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/commit/cccd798027f0a20db796b3df6c64f9897a39d7b1"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/microsoft/kiota"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/releases/tag/v1.32.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22", "CWE-829", "CWE-918" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T16:10:17Z",
    "nvd_published_at" : "2026-07-16T16:19:15Z"
  }
}