CVE-2026-59863: Microsoft.OpenApi.Kiota Out-of-repo File Write + Generation-time Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4rj6-vrwv-wr8m",
  "modified" : "2026-08-17T14:54:18Z",
  "published" : "2026-07-24T16:11:24Z",
  "aliases" : [ "CVE-2026-59863" ],
  "summary" : "Microsoft Kiota Workspace-config poisoning: out-of-repo file write + generation-time SSRF",
  "details" : "### Summary\n\nMicrosoft Kiota honors a poisoned `.kiota/workspace.json` — the workspace configuration that Kiota's\ndocumented team workflow has developers commit to their repository — **unvalidated** on\n`kiota client generate` / `kiota plugin generate`. A repository (or pull request) containing a malicious\nper-client / per-plugin `outputPath` causes Kiota, when a developer or CI runs the documented regenerate\ncommand, to **(CWE-22) write the entire generated client to an arbitrary path outside the workspace** — the\n`outputPath` was not confined to the workspace root and absolute paths were accepted.\n\nConfirmed on Kiota **1.32.4** (`KIOTA_CONFIG_PREVIEW=true`, the self-contained `linux-x64` release binary).\n\n### Details\n\n```jsonc\n// .kiota/workspace.json (committed to the repo)\n\"clients\": { \"MyClient\": {\n   \"outputPath\": \"/abs/path/outside/repo/pwned_client\"   // -> generated client written here (CWE-22)\n}}\n```\n\nRunning `kiota client generate --client-name MyClient` in the repo writes `MyClient.cs`,\n`P/PRequestBuilder.cs`, … to the attacker-chosen `outputPath` (verified outside the working tree).\n\n#### Note on `descriptionLocation`\n\nThe per-consumer `descriptionLocation` is intentionally fetched at generation time — this is how Kiota knows\nwhere to pull an updated description from when refreshing a client, the same way any other value in a\ncommitted lock/config file is honored. It is **not** treated as a vulnerability and is unchanged; only\n`outputPath` is now confined.\n\n### Impact\n\nA malicious or compromised repository — or a malicious PR that edits `.kiota/workspace.json` — leads to\narbitrary file write on the developer's or CI host's filesystem (overwrite source/build files, drop files in\nauto-loaded locations) whenever a teammate clones/pulls and runs the documented `kiota client generate` /\n`kiota plugin generate` to refresh the client. CWE-22.\n\nThis is a different trust boundary from the OpenAPI-description-based findings: the malicious input is the\nKiota **config**, not the spec.\n\n### Patches\n\nFixed in **1.29.1 and 1.32.5** (https://github.com/microsoft/kiota/pull/7885). On loading a workspace configuration,\neach client/plugin `outputPath` is validated to be a relative subdirectory of the workspace: null/empty,\nrooted paths (POSIX `/`, UNC `\\\\` / `//`, Windows drive `X:\\`), and any `..` traversal segment are rejected,\nand the resolved full path must stay under the workspace root. Generation aborts with an error if any\nconsumer's `outputPath` escapes the workspace.\n\n### Remediation\n\nUpgrade to Kiota **1.29.1, 1.32.5** or later. Review any committed workspace configs for `outputPath` values that\npoint outside the workspace.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:H/VA:L/SC:N/SI:N/SA: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-4rj6-vrwv-wr8m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-59863"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/pull/7885"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/commit/4049327872db7846ace35c9003774d3e3878e4e9"
  }, {
    "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" : "2026-07-24T16:11:24Z",
    "nvd_published_at" : "2026-07-16T15:16:35Z"
  }
}