CVE-2026-8204

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

Score 5.3 from GitHub Security Advisory published 2026-05-21. NVD baseline CVSS 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: None knownExposed: 0

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

Concrete CMS 9.5.0 and below is vulnerable to authorization Bypass in the Calendar Event Frontend Dialog which can allow cross-calendar data disclosure. A public calendar block can be used as a pivot point to access private calendar data. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
24(Track)
EG Risk 24/100SSVC: 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
Severity53% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
11%
KEV
Not listed

Published

May 21, 2026

Last Modified

July 23, 2026

Advisory Details (1)

Auto-updated Jun 16, 2026
No patch confirmed yet.
generic

9.5.1 Release Notes :: Concrete CMS

https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes

Vendor Advisories for CVE-2026-8204(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Packagist(1)
PackageVulnerable rangeFixed inDependents
concrete5/concrete58.0 ... 9.5.0RC2 (89 versions)9.5.1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 46× 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 145 total refreshes for this CVE.

  1. 2026-08-27 14:25 UTCEPSS rescore
  2. 2026-08-26 14:47 UTCEPSS rescore
  3. 2026-08-25 13:49 UTCEPSS rescore
  4. 2026-08-24 14:18 UTCEPSS rescore
  5. 2026-08-23 16:46 UTCEG score recompute
  6. 2026-08-21 23:49 UTCEPSS rescore
  7. 2026-08-21 21:44 UTCEG score recompute
  8. 2026-08-20 22:56 UTCEPSS rescore
  9. 2026-08-20 18:43 UTCEG score recompute
  10. 2026-08-19 17:04 UTCEPSS rescore
  11. 2026-08-18 13:49 UTCEPSS rescore
  12. 2026-08-18 13:49 UTCEPSS rescore
  13. 2026-08-17 13:47 UTCEPSS rescore
  14. 2026-08-17 09:47 UTCEG score recompute
  15. 2026-08-16 14:56 UTCEPSS rescore
  16. 2026-08-16 14:56 UTCEPSS rescore
  17. 2026-08-16 03:22 UTCEG score recompute
  18. 2026-08-16 02:15 UTCEPSS rescore
  19. 2026-08-14 05:41 UTCEG score recompute
  20. 2026-08-13 22:00 UTCEPSS rescore
  21. 2026-08-13 08:04 UTCEG score recompute
  22. 2026-08-12 13:51 UTCEPSS rescore
  23. 2026-08-12 09:50 UTCEG score recompute
  24. 2026-08-11 13:43 UTCEPSS rescore
  25. 2026-08-11 07:45 UTCEG score recompute
Show 75 more
  1. 2026-08-11 00:00 UTCEPSS rescore
  2. 2026-08-10 10:08 UTCEG score recompute
  3. 2026-08-09 13:47 UTCEPSS rescore
  4. 2026-08-09 12:31 UTCEG score recompute
  5. 2026-08-08 16:37 UTCEPSS rescore
  6. 2026-08-06 18:49 UTCEG score recompute
  7. 2026-08-06 13:47 UTCEPSS rescore
  8. 2026-08-05 21:12 UTCEG score recompute
  9. 2026-08-05 19:17 UTCEPSS rescore
  10. 2026-08-05 19:17 UTCEPSS rescore
  11. 2026-08-04 15:10 UTCEPSS rescore
  12. 2026-08-04 10:39 UTCEPSS rescore
  13. 2026-08-03 16:50 UTCEG score recompute
  14. 2026-08-03 10:36 UTCEPSS rescore
  15. 2026-08-02 15:00 UTCEG score recompute
  16. 2026-08-02 02:27 UTCEPSS rescore
  17. 2026-08-01 17:23 UTCEG score recompute
  18. 2026-08-01 04:16 UTCEPSS rescore
  19. 2026-07-30 16:28 UTCEPSS rescore
  20. 2026-07-30 01:30 UTCEPSS rescore
  21. 2026-07-29 17:41 UTCEG score recompute
  22. 2026-07-28 15:37 UTCEPSS rescore
  23. 2026-07-27 14:14 UTCEPSS rescore
  24. 2026-07-26 14:54 UTCEPSS rescore
  25. 2026-07-26 08:08 UTCEG score recompute
  26. 2026-07-25 14:18 UTCEPSS rescore
  27. 2026-07-24 14:18 UTCEPSS rescore
  28. 2026-07-23 14:18 UTCEPSS rescore
  29. 2026-07-23 03:23 UTCEG score recompute
  30. 2026-07-22 14:08 UTCEPSS rescore
  31. 2026-07-21 15:25 UTCEPSS rescore
  32. 2026-07-21 15:25 UTCEPSS rescore
  33. 2026-07-20 17:08 UTCEPSS rescore
  34. 2026-07-19 14:31 UTCEPSS rescore
  35. 2026-07-19 02:29 UTCEPSS rescore
  36. 2026-07-18 10:04 UTCEPSS rescore
  37. 2026-07-17 21:59 UTCOSV refresh
  38. 2026-07-16 17:03 UTCEPSS rescore
  39. 2026-07-15 16:57 UTCEPSS rescore
  40. 2026-07-15 02:00 UTCEPSS rescore
  41. 2026-07-13 22:31 UTCEPSS rescore
  42. 2026-07-13 06:13 UTCEPSS rescore
  43. 2026-07-12 05:46 UTCEPSS rescore
  44. 2026-07-11 08:27 UTCEPSS rescore
  45. 2026-07-09 19:10 UTCEPSS rescore
  46. 2026-07-08 15:16 UTCEPSS rescore
  47. 2026-07-08 15:16 UTCEPSS rescore
  48. 2026-07-07 13:46 UTCEPSS rescore
  49. 2026-07-07 13:46 UTCEPSS rescore
  50. 2026-07-06 16:27 UTCEPSS rescore
  51. 2026-07-06 16:27 UTCEPSS rescore
  52. 2026-07-06 02:23 UTCEPSS rescore
  53. 2026-07-06 02:23 UTCEPSS rescore
  54. 2026-07-05 02:31 UTCEPSS rescore
  55. 2026-07-05 02:30 UTCEPSS rescore
  56. 2026-07-04 06:31 UTCEPSS rescore
  57. 2026-07-04 06:31 UTCEPSS rescore
  58. 2026-07-01 15:07 UTCEPSS rescore
  59. 2026-06-30 23:22 UTCEPSS rescore
  60. 2026-06-29 14:06 UTCEPSS rescore
  61. 2026-06-28 14:07 UTCEPSS rescore
  62. 2026-06-28 04:56 UTCEPSS rescore
  63. 2026-06-27 03:08 UTCEPSS rescore
  64. 2026-06-25 13:50 UTCEPSS rescore
  65. 2026-06-24 14:05 UTCEPSS rescore
  66. 2026-06-23 21:33 UTCEPSS rescore
  67. 2026-06-22 14:25 UTCEPSS rescore
  68. 2026-06-21 14:56 UTCEPSS rescore
  69. 2026-06-21 01:59 UTCEPSS rescore
  70. 2026-06-19 19:26 UTCEPSS rescore
  71. 2026-06-18 17:52 UTCEPSS rescore
  72. 2026-06-17 19:57 UTCGHSA enrichment
  73. 2026-06-17 17:53 UTCEPSS rescore
  74. 2026-06-16 20:32 UTCGHSA enrichment
  75. 2026-06-16 17:53 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-8204?
CVE-2026-8204 is a medium vulnerability published on May 21, 2026. Concrete CMS 9.5.0 and below is vulnerable to authorization Bypass in the Calendar Event Frontend Dialog which can allow cross-calendar data disclosure. A public calendar block can be used as a pivot point to access private calendar data. The Concrete CMS security team gave this vulnerability a…
When was CVE-2026-8204 disclosed?
CVE-2026-8204 was first published in the National Vulnerability Database on May 21, 2026, with the most recent update on July 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-8204 actively exploited?
CVE-2026-8204 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 88.7% of all scored CVEs.
What is the CVSS score of CVE-2026-8204?
CVE-2026-8204 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-8204?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-8204, 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.

Dependency Blast Radius

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