Firefly III - Webhook URL Validation Explicitly Allows Loopback and Is Bypassable via DNS Rebinding (CVE-2026-71250) | HOL Guard CVE

Medium · CVSS 4.3CVE-2026-71250

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

Answer in brief

CVE-2026-71250 records a Medium severity (CVSS 4.3) vulnerability in Firefly III - Webhook URL Validation Explicitly Allows Loopback and Is Bypassable via DNS Rebinding. The current sources do not mark it as known exploited. The current feed maps firefly-iii/firefly-iii (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 5, 2026Updated Aug 26, 2026Source checked Sep 20, 2026First seen by HOL Aug 5, 2026Material review Aug 26, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 4.3
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

CVSS is 4.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps firefly-iii/firefly-iii (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
firefly-iii/firefly-iiigeneric	0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for firefly-iii/firefly-iii.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 5, 2026

Sources and claim methodology

GitHub security advisorygithub.com

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.