CVE-2026-59863 — Vulnerability in Microsoft.OpenApi.Kiota — CVE...

### Summary Microsoft Kiota honors a poisoned `.kiota/workspace.json` — the workspace configuration that Kiota's documented team workflow has developers commit to their repository — **unvalidated** on `kiota client generate` / `kiota plugin generate`. A repository (or pull request) containing a malicious per-client / per-plugin `outputPath` causes Kiota, when a developer or CI runs the documented regenerate command, to **(CWE-22) write the entire generated client to an arbitrary path outside the workspace** — the `outputPath` was not confined to the workspace root and absolute paths were accepted. Confirmed on Kiota **1.32.4** (`KIOTA_CONFIG_PREVIEW=true`, the self-contained `linux-x64` release binary). ### Details ```jsonc // .kiota/workspace.json (committed to the repo) "clients": { "MyClient": { "outputPath": "/abs/path/outside/repo/pwned_client" // -> generated client written here (CWE-22) }} ``` Running `kiota client generate --client-name MyClient` in the repo writes `MyClient.cs`, `P/PRequestBuilder.cs`, … to the attacker-chosen `outputPath` (verified outside the working tree). #### Note on `descriptionLocation` The per-consumer `descriptionLocation` is intentionally fetched at generation time — this is how Kiota knows where to pull an updated description from when refreshing a client, the same way any other value in a committed lock/config file is honored. It is **not** treated as a vulnerability and is unchanged; only `outputPath` is now confined. ### Impact A malicious or compromised repository — or a malicious PR that edits `.kiota/workspace.json` — leads to arbitrary file write on the developer's or CI host's filesystem (overwrite source/build files, drop files in auto-loaded locations) whenever a teammate clones/pulls and runs the documented `kiota client generate` / `kiota plugin generate` to refresh the client. CWE-22. This is a different trust boundary from the OpenAPI-description-based findings: the malicious input is the Kiota **config**, not the spec. ### Patches Fixed in **1.29.1 and 1.32.5** (https://github.com/microsoft/kiota/pull/7885). On loading a workspace configuration, each client/plugin `outputPath` is validated to be a relative subdirectory of the workspace: null/empty, rooted paths (POSIX `/`, UNC `\\` / `//`, Windows drive `X:\`), and any `..` traversal segment are rejected, and the resolved full path must stay under the workspace root. Generation aborts with an error if any consumer's `outputPath` escapes the workspace. ### Remediation Upgrade to Kiota **1.29.1, 1.32.5** or later. Review any committed workspace configs for `outputPath` values that point outside the workspace.