Unleash: Addon webhook URL is dialed server-side with no internal-address filtering, enabling SSRF to internal services / cloud metadata and exfiltration of configured request headers

Summary

Unleash's addon/integration subsystem lets an operator configure a webhook (and the Slack, Microsoft Teams, Datadog, and New Relic integrations) with a target url parameter. Whenever a subscribed feature-flag event fires, the Unleash server itself issues an HTTP request to that configured URL. The URL is taken verbatim from the addon's parameters.url and passed straight to the HTTP client (ky) with no validation of the host: there is no allow-list, no deny-list, and no blocking of loopback, link-local, RFC1918, or cloud-metadata addresses anywhere in the addon code path. A principal able to create or update an addon can therefore point the server at an internal-only URL — for example http://169.254.169.254/latest/meta-data/… (cloud IMDS), http://127.0.0.1: /… (a service bound to localhost), or any RFC1918 host — and cause the Unleash server to dial it from inside the trust boundary.

The request is blind (the response body is not returned to the caller), but the addon records whether the request succeeded and its HTTP status into the integration-event log, giving a status/timing oracle for probing internal services. In addition, the webhook provider forwards the operator-configured Authorization header and arbitrary customHeaders to whatever host the url points at (Datadog forwards DD-API-KEY), so an attacker who controls or can observe the target host also obtains those secrets. The full feature-event JSON is POSTed to the chosen internal endpoint as the request body.

Creating/updating addons is gated by the root permissions CREATE_ADDON / UPDATE_ADDON. These are not the super-admin ADMIN permission and not project-scoped; an instance admin can place them in a custom root role and delegate them to a non-super-admin user, who then has exactly enough privilege to weaponize the integration into an SSRF primitive without holding full admin. This bounds the finding to an authenticated, addon-management-privileged actor (reflected in PR:H), which is the honest precondition.

Affected code (v8.0.0)

The base addon issues the outbound request with the raw URL and no host checks (src/lib/addons/addon.ts):

async fetchRetry(
    url: string,
    options: any = {},
    retries: number = 1,
): PromiseResponse> {
    try {
        const res = await ky(url, {            // 
            retry: retries,
            ...options,
        });
        return res;
    } catch (e) {
        const { method } = options;
        this.logger.warn(`Error querying ${url} ...`, e);
        return { status: e.code, ok: false } as Response;
    }
}