New API: SSRF Protection Bypass via Unresolved Hostname in Notification URLs

Summary

The default SSRF protection configuration did not apply IP filtering to hostnames. With ApplyIPFilterForDomain disabled by default, URL validation checked domain allow/block rules but did not resolve a hostname and validate the resolved IP address. Authenticated users could configure notification URLs for Webhook, Bark, or Gotify notifications and point a hostname at an internal or metadata IP address.

Impact

A regular authenticated user could cause the server to send notification requests to internal HTTP services reachable from the deployment network. Depending on the target environment, this could expose sensitive internal data through timing, errors, or response-dependent behavior. The issue is rated High.

Affected versions

Versions before v0.12.0-alpha.1 are affected. The previous affected range of <= v0.11.4-alpha.4 was too narrow because the unsafe default remained present until the v0.12.0-alpha.1 fix.

Patches

This issue is fixed in v0.12.0-alpha.1. The default fetch setting now sets ApplyIPFilterForDomain: true, causing hostname destinations to be resolved and checked against the configured IP filtering rules during URL validation.

This patch addresses the unresolved-hostname bypass for the affected notification URL paths. It does not mark the separate DNS rebinding advisory as fixed, because connection-time IP enforcement is tracked separately.

Workarounds

If upgrading immediately is not possible, explicitly enable ApplyIPFilterForDomain, restrict notification URL domains with an allowlist, disable user-configurable notification URLs where practical, and enforce outbound network filtering at the host or network layer.

Resources

• Fixed by commit 20399d3c8fcb4e3649d53163eb11940fd6763743.
• Relevant code paths: setting/system_setting/fetch_setting.go, common/ssrf_protection.go, service/webhook.go, and service/user_notify.go.