GHSA-8q49-2h5h-434x: FrontMCP Server-Side Request Forgery (SSRF) Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-8q49-2h5h-434x",
  "modified" : "2026-07-24T22:40:00Z",
  "published" : "2026-07-24T22:40:00Z",
  "aliases" : [ ],
  "summary" : "FrontMCP: Server-Side Request Forgery (SSRF) in the OpenAPI adapter spec-change poller",
  "details" : "## Summary\n\nThe OpenAPI adapter's spec-change **poller** (`OpenApiSpecPoller`) re-fetched the\nconfigured spec `url` on a timer using a raw global `fetch()`, bypassing the SSRF\nguard (`safeFetch` / `assertUrlSafe`) that `OpenAPIToolGenerator.fromURL()` applies\nto the initial spec load. As a result, the pinning/DNS-resolution hardening delivered\nvia `mcp-from-openapi >= 2.5.0` (advisory GHSA-65h7-9wrw-629c) protected the initial\nload but **not** the recurring poll of the same URL. When polling is enabled against\nan untrusted or attacker-influenceable spec URL, this is an unguarded SSRF vector.\n\n## Details\n\nThe initial spec load is guarded. `OpenapiAdapter` resolves a secure `refResolution`\npolicy and passes it to the guarded loader:\n\n```ts\n// libs/adapters/src/openapi/openapi.adapter.ts — initializeGenerator()\nreturn await OpenAPIToolGenerator.fromURL(this.options.url, {\n  // ...\n  followRedirects: this.options.loadOptions?.followRedirects ?? false,\n  refResolution, // secure default: external $refs off, internal targets blocked\n});\n```\n\nBut the poller — which re-fetches **the same URL** on every interval — did not:\n\n```ts\n// libs/adapters/src/openapi/openapi-spec-poller.ts — doFetch() (vulnerable, <= 1.5.5)\nconst controller = new AbortController();\nconst timeout = setTimeout(() => controller.abort(), this.fetchTimeoutMs);\ntry {\n  const response = await fetch(this.url, {   // <-- raw global fetch, no SSRF guard\n    headers,\n    signal: controller.signal,\n  });\n  // ...hash the body, fire onChanged...\n}\n```\n\nBecause `doFetch()` never called `safeFetch`, none of the guard's protections applied\nto the polled request:\n\n- no allow-list / block-list enforcement (`allowedHosts` / `blockedHosts`);\n- no internal/private/loopback/link-local/CGNAT/cloud-metadata IP blocking;\n- no DNS resolution of the hostname (so a DNS name that resolves to an internal IP,\n  e.g. `http://127.0.0.1.nip.io/`, was reached);\n- no connection **pinning** to the validated IP (DNS-rebinding TOCTOU);\n- no per-hop re-validation of HTTP redirects.\n\nThis is the identical threat model to `fromURL()` / external `$ref` resolution\n(GHSA-65h7-9wrw-629c), applied to a request path that the fix for that advisory did\nnot cover.\n\n## Impact\n\nA server that enables spec polling against an untrusted or attacker-influenceable\nspec URL will, on every poll interval, issue a server-side `GET` to whatever host the\nURL (or a DNS name it resolves to, or a redirect it returns) points at — including\ninternal-only addresses unreachable from the public internet. Consequences include:\n\n- reading cloud-instance metadata endpoints (e.g. `169.254.169.254`) — credential /\n  token theft;\n- probing and reaching internal services and private-range hosts (internal network\n  scanning);\n- DNS-rebinding to swap a public host for an internal one between validation and\n  connection.\n\nThe poller issues `GET` requests only, so the primary impact is **confidentiality**\n(reaching and reading internal endpoints); the fetched body is content-hashed to\ndetect change and the subsequent tool rebuild goes back through the guarded\n`fromURL()` path.\n\n## Preconditions\n\nExploitation requires **both**:\n\n1. `polling.enabled: true` on an `OpenapiAdapter` (polling is off by default and\n   requires the URL-based `url` option, not an inline `spec`); **and**\n2. the spec `url` is untrusted / attacker-influenceable (e.g. it is derived from user\n   input, a tenant-supplied value, or otherwise not a fixed trusted constant), or an\n   otherwise-trusted spec host is attacker-controlled or can redirect.\n\nServers that poll a fixed, trusted, first-party spec URL are not exposed in practice,\nthough they still benefit from the guard as defense-in-depth.\n\n## Proof of concept\n\n```ts\nimport { OpenapiAdapter } from '@frontmcp/adapters';\n\n// url is attacker-influenceable and points (directly, via DNS, or via redirect)\n// at an internal target; polling re-fetches it every interval.\nconst adapter = OpenapiAdapter.init({\n  name: 'evil',\n  url: 'http://169.254.169.254/latest/meta-data/', // or http://127.0.0.1.nip.io/...\n  polling: { enabled: true, intervalMs: 5000 },\n});\n\nawait adapter.fetch();   // initial load IS guarded (blocked)\nadapter.startPolling();  // <= 1.5.5: each poll issues an UNGUARDED GET to the internal target\n```\n\nOn `<= 1.5.5` the timed poll reaches the internal address. On the patched version the\npoll fails closed (no request is made; the failure is logged) exactly as the initial\nload does.\n\n## Patch\n\nThe fix routes the poller through the same SSRF guard as the initial load, with the\nsame policy, so both paths share one DNS resolution + connection pinning and cannot\ndiverge:\n\n- `OpenApiSpecPoller.doFetch()` now calls `safeFetch(this.url, { headers, timeoutMs,\n  followRedirects, ssrf })` from `mcp-from-openapi` instead of the global `fetch()`.\n- `OpenapiAdapter.startPolling()` injects the adapter's resolved policy into the\n  poller: `ssrf: normalizeSsrfOptions(this.resolveRefResolution())` and\n  `followRedirects: loadOptions?.followRedirects ?? false` — identical to what\n  `fromURL()` receives.\n- `SpecPollerOptions` gained optional `ssrf` / `followRedirects`; standalone use of\n  `OpenApiSpecPoller` defaults to the secure policy (internal targets blocked,\n  redirects not followed).\n\nFiles changed:\n\n- `libs/adapters/src/openapi/openapi-spec-poller.ts`\n- `libs/adapters/src/openapi/openapi-spec-poller.types.ts`\n- `libs/adapters/src/openapi/openapi.adapter.ts`\n\nRequires `mcp-from-openapi >= 2.5.0` (already a dependency at `2.5.1`), which exports\n`safeFetch` / `normalizeSsrfOptions` and performs the resolved-IP validation and\nconnection pinning.\n\n## Remediation\n\nUpgrade `@frontmcp/adapters` to `1.5.6` or later. No configuration change is required:\npolling now inherits the same secure defaults as the initial spec load (external\ntargets blocked, redirects not followed). To poll a genuinely internal or localhost\nspec server in a trusted environment, opt in explicitly with\n`loadOptions.refResolution.allowInternalIPs: true` — the same knob that gates the\ninitial load.\n\n## Workarounds\n\nFor users who cannot upgrade immediately:\n\n- disable polling (`polling.enabled: false`) on adapters whose spec `url` is not a\n  fixed, trusted, first-party value; or\n- only enable polling against spec URLs you fully control, served over HTTPS from a\n  host that cannot be made to redirect to internal targets; and\n- enforce network egress controls / an allow-list at the platform layer so the server\n  cannot reach internal ranges or cloud-metadata endpoints.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@frontmcp/adapters"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.5.6"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.5.5"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/agentfront/frontmcp/security/advisories/GHSA-8q49-2h5h-434x"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/agentfront/frontmcp/pull/510"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/agentfront/frontmcp/commit/077201e109bf6f45dbc85c36d6bd77ded18ab13e"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/agentfront/frontmcp"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/agentfront/frontmcp/releases/tag/v1.5.6"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-918" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T22:40:00Z",
    "nvd_published_at" : null
  }
}