FOSSBilling: Authentication bypass allows unauthenticated administrator creation (CVE-2026-33543) | HOL Guard CVE

Critical · CVSS 9.3CVE-2026-33543

FOSSBilling: Authentication bypass allows unauthenticated administrator creation

Answer in brief

CVE-2026-33543 records a Critical severity (CVSS 9.3) vulnerability in FOSSBilling: Authentication bypass allows unauthenticated administrator creation. The current sources do not mark it as known exploited. The current feed maps FOSSBilling/FOSSBilling (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 Jun 24, 2026Updated Jun 25, 2026Source checked Sep 19, 2026First seen by HOL Jun 24, 2026Material review Jun 25, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.3
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 9.3. 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 FOSSBilling/FOSSBilling (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
FOSSBilling/FOSSBillinggeneric	< 0.8.0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for FOSSBilling/FOSSBilling.
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
Jun 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Jun 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jun 24, 2026

Sources and claim methodology

Upstream source description

FOSSBilling is a free, open-source billing and client management system. Versions 0.7.2 and prior expose a guest API endpoint, /api/guest/staff/create, intended for initial administrator bootstrap. Due to a flawed admin-existence check, the endpoint remains usable after an administrator already exists. The flawed guard check uses is_countable() on a value that returns a Model_Admin object or null rather than a countable type, causing the expression to always evaluate as true and bypass the intended protection. As a result, an attacker can reach the unprotected endpoint to create a new administrator account and immediately authenticate, gaining a fully privileged admin session even when an admin already exists. This issue has been fixed in version 0.8.0.

Quoted source text, attributed separately from HOL analysis.