CVE-2026-71250
Firefly III: Webhook URL Validation Explicitly Allows Loopback and Is Bypassable via DNS Rebinding
Firefly III's webhook URL validator (IsValidWebhookUrl.php) filters most private/reserved IPv4 ranges but contains an explicit early-return that allows any resolved address in 127.0.0.0/8, permitting an authenticated user (with webhooks enabled, which is off by default) to configure a webhook targeting loopback services on the server. Additionally, the validator resolves the target hostname once via gethostbyname() at validation time, but the actual outbound request (StandardWebhookSender.php, via Guzzle) re-resolves the hostname independently at send time, allowing a DNS-rebinding attacker to pass validation against a public IP and have the real request delivered to a private or internal address. The webhook response body is only written to a server-side debug log, not returned to the triggering user, so this is a blind SSRF primitive rather than one with direct response read-back.
| CWE | CWE-918 |
| Vendor | firefly-iii |
| Product | firefly-iii |
| Published | Aug 5, 2026 |
| Last Updated | Aug 5, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N