CVE-2026-71250

Firefly III - Webhook URL Validation Explicitly Allows Loopback and Is Bypassable via DNS Rebinding

Published Aug 5, 2026 CVSS 3.1 · 4.3 Medium EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

No advisories available
References
History
Type Values Removed Values Added
Description 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. 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.
Type Values Removed Values Added
Title Firefly III: Webhook URL Validation Explicitly Allows Loopback and Is Bypassable via DNS Rebinding Firefly III - Webhook URL Validation Explicitly Allows Loopback and Is Bypassable via DNS Rebinding
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Firefly-iii
Firefly-iii firefly Iii
Vendors & Products Firefly-iii
Firefly-iii firefly Iii
Type Values Removed Values Added
Description 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.
Title Firefly III: Webhook URL Validation Explicitly Allows Loopback and Is Bypassable via DNS Rebinding
Weaknesses CWE-918
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
TuranSec
Published
Updated
Aug 10, 2026, 11:46 AM
Reserved
Aug 5, 2026, 10:53 AM
Status
Deferred
Published
Aug 5, 2026, 11:16 AM
Modified
Aug 26, 2026, 5:13 PM