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: 0.4%, top 63% 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
9.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.3Exploit: None knownExposed: 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)
EG Risk
47(Track)
EG Risk 47/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity93% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
38%
KEV
Not listed

Published

June 24, 2026

Last Modified

June 25, 2026

Advisory Details (2)

Auto-updated Sep 3, 2026
Patch available. Sources: github, github_release.
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 7× in last 7d / 43× 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 118 total refreshes for this CVE.

  1. 2026-09-11 14:53 UTCEPSS rescore
  2. 2026-09-11 09:37 UTCEPSS rescore
  3. 2026-09-10 09:34 UTCEPSS rescore
  4. 2026-09-08 22:00 UTCEPSS rescore
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  11. 2026-09-01 04:39 UTCEPSS rescore
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  13. 2026-08-30 19:50 UTCEG score recompute
  14. 2026-08-30 19:17 UTCEPSS rescore
  15. 2026-08-30 01:22 UTCEPSS rescore
  16. 2026-08-28 21:41 UTCEPSS rescore
  17. 2026-08-28 02:59 UTCEG score recompute
  18. 2026-08-27 14:25 UTCEPSS rescore
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  20. 2026-08-25 13:49 UTCEPSS rescore
  21. 2026-08-24 21:54 UTCEG score recompute
  22. 2026-08-24 14:17 UTCEPSS rescore
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  24. 2026-08-23 03:19 UTCEG score recompute
  25. 2026-08-23 00:19 UTCEPSS rescore
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  1. 2026-08-22 11:15 UTCEG score recompute
  2. 2026-08-21 23:49 UTCEPSS rescore
  3. 2026-08-21 00:55 UTCEG score recompute
  4. 2026-08-20 22:55 UTCEPSS rescore
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  6. 2026-08-20 07:14 UTCEG score recompute
  7. 2026-08-19 17:03 UTCEPSS rescore
  8. 2026-08-19 01:44 UTCEG score recompute
  9. 2026-08-18 13:48 UTCEPSS rescore
  10. 2026-08-17 13:47 UTCEPSS rescore
  11. 2026-08-16 15:41 UTCEG score recompute
  12. 2026-08-16 14:56 UTCEPSS rescore
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  15. 2026-08-15 05:09 UTCEG score recompute
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  17. 2026-08-13 22:55 UTCEG score recompute
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  19. 2026-08-12 18:04 UTCEG score recompute
  20. 2026-08-12 13:50 UTCEPSS rescore
  21. 2026-08-11 16:10 UTCEG score recompute
  22. 2026-08-11 03:12 UTCEG score recompute
  23. 2026-08-11 00:00 UTCEPSS rescore
  24. 2026-08-09 16:15 UTCEG score recompute
  25. 2026-08-09 13:46 UTCEPSS rescore
  26. 2026-08-08 18:41 UTCEG score recompute
  27. 2026-08-08 16:37 UTCEPSS rescore
  28. 2026-08-07 16:47 UTCEG score recompute
  29. 2026-08-06 14:54 UTCEG score recompute
  30. 2026-08-06 13:46 UTCEPSS rescore
  31. 2026-08-05 21:33 UTCEG score recompute
  32. 2026-08-05 19:17 UTCEPSS rescore
  33. 2026-08-04 19:28 UTCEG score recompute
  34. 2026-08-04 15:10 UTCEPSS rescore
  35. 2026-08-04 15:09 UTCEG score recompute
  36. 2026-08-04 10:38 UTCEPSS rescore
  37. 2026-08-02 05:14 UTCEG score recompute
  38. 2026-08-02 02:27 UTCEPSS rescore
  39. 2026-08-01 07:38 UTCEG score recompute
  40. 2026-08-01 04:16 UTCEPSS rescore
  41. 2026-07-30 19:20 UTCEG score recompute
  42. 2026-07-30 16:28 UTCEPSS rescore
  43. 2026-07-30 14:51 UTCEG score recompute
  44. 2026-07-30 02:09 UTCEG score recompute
  45. 2026-07-30 01:30 UTCEPSS rescore
  46. 2026-07-29 00:39 UTCEG score recompute
  47. 2026-07-27 17:32 UTCEG score recompute
  48. 2026-07-27 14:13 UTCEPSS rescore
  49. 2026-07-26 15:23 UTCEG score recompute
  50. 2026-07-26 14:54 UTCEPSS rescore
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  52. 2026-07-25 14:18 UTCEPSS rescore
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  56. 2026-07-23 14:18 UTCEPSS rescore
  57. 2026-07-23 14:18 UTCEPSS rescore
  58. 2026-07-23 03:09 UTCEG score recompute
  59. 2026-07-22 14:08 UTCEPSS rescore
  60. 2026-07-21 15:24 UTCEPSS rescore
  61. 2026-07-20 17:08 UTCEPSS rescore
  62. 2026-07-19 14:31 UTCEPSS rescore
  63. 2026-07-19 02:29 UTCEPSS rescore
  64. 2026-07-18 10:04 UTCEPSS rescore
  65. 2026-07-16 17:03 UTCEPSS rescore
  66. 2026-07-15 16:57 UTCEPSS rescore
  67. 2026-07-15 16:57 UTCEPSS rescore
  68. 2026-07-15 02:00 UTCEPSS rescore
  69. 2026-07-13 22:30 UTCEPSS rescore
  70. 2026-07-13 06:13 UTCEPSS rescore
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  72. 2026-07-12 05:46 UTCEPSS rescore
  73. 2026-07-11 08:27 UTCEPSS rescore
  74. 2026-07-09 19:10 UTCEPSS rescore
  75. 2026-07-08 15:15 UTCEPSS rescore

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 0% probability of exploitation in the next 30 days, which ranks it in the top 62.3% of all scored CVEs.
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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