CVE-2026-33543

CRITICALPre-NVD 9.39.3—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 79% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
9.3
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.3
EG Score
9.3(medium)
EPSS
20.7%
KEV
Not listed

Published

June 24, 2026

Last Modified

June 25, 2026

Advisory Details (2)

Auto-updated Jun 24, 2026
Patch available. Sources: github_release, github.
github Patch Available

Authentication bypass allows unauthenticated administrator creation · Advisory · FOSSBilling/FOSSBilling · GitHub

https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-28mh-j262-q49w
github_release Patch Available

0.8.0

Patch available: FOSSBilling/FOSSBilling 0.8.0

https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.0

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 47× in last 7d / 117× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 117 total refreshes for this CVE.

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Frequently asked(5)

What is CVE-2026-33543?
CVE-2026-33543 is a critical vulnerability published on June 24, 2026. 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…
When was CVE-2026-33543 disclosed?
CVE-2026-33543 was first published in the National Vulnerability Database on June 24, 2026, with the most recent update on June 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33543 actively exploited?
CVE-2026-33543 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 20.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-33543?
CVE-2026-33543 has a CVSS v3 base score of 9.3 (NVD).
How do I remediate CVE-2026-33543?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33543, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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