GHSA-7rx3-5wx3-5v76 Nebula-mesh allows non-admin operators to disable webhook SSRF protection via `allow_private`
SummaryNon-admin operators (role `user`) can set `allow_private: true` on their own managed webhook subscription (`POST`/`PATCH /api/v1/webhook-subscriptions`). No admin check exists on this field. At delivery time, `allow_private` switches the dispatcher to an unguarded HTTP client, bypassing the private/loopback/link-local SSRF guard — letting a low-privilege operator make the server request internal addresses.Details`internal/api/webhooks.go:67` (`handleCreateWebhookSubscription`) and `:110` (`handleUpdateWebhookSubscription`) persist operator-supplied `AllowPrivate` with no role check — only ownership is enforced (`canAccessWebhookSub`), and that's not even called on create.`internal/webhook/webhook.go:294-296`:`d.unguarded` skips the loopback/private/link-local rejection `config.ValidateWebhookURL` otherwise enforces.Every other tenant-impacting toggle (network create `internal/api/networks.go:21`, settings PATCH `internal/api/settings.go:36`, CA management) gates on `isActiveAdmin`. `allow_private` is the exception — introduced with managed webhook subscriptions (PR #258) and missed by the two prior fixes for the same authz-gap class in this repo (GHSA-598g-h2vc-h5vg, GHSA-c6v2-3ffm-vcmc).PoCVerified live against a real running instance of nebula-mesh (HEAD `2c3457c`, built and run locally, no third-party requests made — the "internal service" below is a loopback listener standing in for one). Setup: `nebula-mgmt init` + `serve` on `127.0.0.1:8181`; admin CLI creates operator `lowpriv` with `-role user` and mints it an API key (`d984bb...c7c`) — the routine, legitimate way any non-admin operator gets access. `lowpriv` self-mints its own CA (`POST /api/v1/cas`, allowed for any operator) and creates a host on a network scoped to that CA, so it owns something it can legitimately act on.**Step 1 — create-side bypass, as the non-admin `lowpriv` operator:**Actual response:`201 Created`, `allow_private:true` persisted, `owner_operator_id` is the non-admin `lowpriv` account (`role: "user"`). No `403 Forbidden` — which is what every comparable admin-gated endpoint (`POST /api/v1/networks`, `PATCH /api/v1/settings`) returns for this same non-admin key.**Control — same non-admin key, same target, `allow_private` omitted (defaults false):**Confirms the guard is real and active for this exact target — `allow_private:true` in Step 1 is what disabled it.**Step 2 — delivery-side SSRF.** A Python `http.server` listener bound `127.0.0.1:9999`, logging every request it receives. `lowpriv` fires a host-lifecycle event on the host it owns:Both returned `200 OK`. The listener received, in real time, two outbound POSTs from the nebula-mesh server itself:Same result holds for `host.enrolled` — any lifecycle event the operator can cause on a resource they own routes through the same dispatcher code path.**Step 3 — reachability oracle:**`last_status`/`last_error` confirm delivery outcome and, on failure, the dial/connection error string — a reachability oracle over internal addresses. The dispatcher's delivery-recording path stores success/failure and error text only, never the target's response body.ImpactA non-admin operator gains server-side request capability against internal-only/loopback addresses, outside the admin boundary the codebase enforces everywhere else. Enables internal reachability probing and blind POST interaction with internal services. May expose cloud IAM credentials on deployments where the metadata service accepts unauthenticated/IMDSv1-style requests — conditional on target config, not guaranteed (IMDSv2's token requirement would block it).
CVSS v3.1 score: 7.7