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[GHSA-4rj6-vrwv-wr8m] Microsoft Kiota Workspace-config poisoning: out-of-repo file write + generation-time SSRF #9148

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[GHSA-4rj6-vrwv-wr8m] Microsoft Kiota Workspace-config poisoning: out-of-repo file write + generation-time SSRF #9148

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8 changes: 4 additions & 4 deletions advisories/github-reviewed/2026/07/GHSA-4rj6-vrwv-wr8m/GHSA-4rj6-vrwv-wr8m.json
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{
"schema_version": "1.4.0",
"id": "GHSA-4rj6-vrwv-wr8m",
"modified": "2026-08-17T14:54:18Z",
"modified": "2026-08-17T14:54:19Z",
"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.",
"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 **1.32.5** (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 **1.32.5** or later. Review any committed workspace configs for `outputPath` values that\npoint outside the workspace.",
"severity": [
{
"type": "CVSS_V4",
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{
"package": {
"ecosystem": "NuGet",
"name": "Microsoft.OpenApi.Kiota"
"name": "Microsoft.OpenApi.Kiota.Builder"
},
"ranges": [
{
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{
"package": {
"ecosystem": "NuGet",
"name": "Microsoft.OpenApi.Kiota.Builder"
"name": "Microsoft.OpenApi.Kiota"
},
"ranges": [
{
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