CVE-2026-76838: Hi.Events before 1.11.1-beta Server-Side Request Forgery via Unvalidated Webhook Redirects
Hi.Events validates a webhook destination only when it is registered, never when it is used. NoInternalUrlRule in backend/app/Validators/Rules/NoInternalUrlRule.php resolves the hostname with gethostbyname() and rejects private and reserved ranges, which any public hostname passes. At dispatch, WebhookDispatchService takes the stored URL and calls it through spatie/laravel-webhook-server without repeating the check, and backend/config/webhook-server.php sets no Guzzle options, so redirect following remains enabled by default. A destination that answers with a redirect to a loopback, private or cloud metadata address therefore causes the server to issue that request, and changing the hostname's DNS record after registration reaches the same result because no resolution is repeated. The response is not discarded: WebhookResponseHandlerService stores the body on the webhook log and WebhookLogResource returns it from the webhook logs endpoint, so the requester reads what the internal service replied rather than inferring it. Both event and organizer webhooks share the rule and the dispatch path. Version 1.11.1-beta revalidates at dispatch, pins the validated address, checks every redirect hop, and decodes IPv6 transition addresses that previously bypassed the filter.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Hi.Eventsto a version that resolves this vulnerability.Fixed in 1.11.1-beta - Configuration
Set Guzzle options in backend/config/webhook-server.php so redirect following is not enabled by default; ensure the server does not follow webhook redirects to loopback, private, or cloud metadata addresses.
Webhook server (backend/config/webhook-server.php) Guzzle redirect following options = disabled (ensure redirect following remains disabled)
Event History
Frequently Asked Questions
Who can exploit this issue?
An attacker needs privileges to register an event or organizer webhook destination. They can supply a publicly resolvable hostname that redirects to an internal address, or later change that hostname’s DNS record to an internal address.
Are default webhook settings affected?
Yes. The webhook server configuration sets no Guzzle options, so redirect following remains enabled by default. The vulnerable flow affects both event and organizer webhooks.
Can an attacker read responses from internal services?
Yes. The webhook response body is stored in the webhook log, and the webhook logs endpoint returns that stored body. This can expose responses from loopback, private-network, or cloud metadata services reached through the SSRF.
What behavior indicates a deployment may be vulnerable?
Deployments before 1.11.1-beta are affected when webhook dispatch uses the stored destination without revalidation. Relevant indicators include webhook destinations using public hostnames that redirect internally or whose DNS resolution has changed since registration.