CVE-2026-18203

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

Score 6.5 from GitHub Security Advisory published 2026-07-31. The CNA's CVSS baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:redhat, epss, ghsa
Trending — 3 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

A flaw was found in the group policy evaluation logic of Keycloak, an identity and access management solution. When a group policy is set to extend permissions to child groups, the system incorrectly uses a simple text-based prefix check to verify group membership. This allows a user who belongs to a different group with a similar starting name to bypass security checks and gain unauthorized access to administrative functions or protected resources.

CVSS v3
6.5
EG Score
6.5MEDIUMmedium confidence
EG Risk
29
EG Risk 29/100CISA SSVC

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
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
21st
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

July 31, 2026

Last Modified

August 31, 2026

Advisory Details (2)

Auto-updated Jul 31, 2026
Patch available. Sources: redhat.
redhat

2508291 – (CVE-2026-18203) CVE-2026-18203 keycloak-services: keycloak-services: Group policy extendChildren matches sibling group path prefixes

https://bugzilla.redhat.com/show_bug.cgi?id=2508291
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-18203

Vendor Advisories for CVE-2026-18203(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 62× 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 167 total refreshes for this CVE.

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

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Frequently asked(5)

What is CVE-2026-18203?
CVE-2026-18203 is a medium vulnerability published on July 31, 2026. A flaw was found in the group policy evaluation logic of Keycloak, an identity and access management solution. When a group policy is set to extend permissions to child groups, the system incorrectly uses a simple text-based prefix check to verify group membership. This allows a user who belongs to…
When was CVE-2026-18203 disclosed?
CVE-2026-18203 was first published on July 31, 2026, with the most recent update on August 31, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-18203 actively exploited?
CVE-2026-18203 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (21st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-18203?
CVE-2026-18203 has a CVSS base score of 6.5 (the CNA's own assessment, by redhat; NVD's own analysis pending).
How do I remediate CVE-2026-18203?
A fix for CVE-2026-18203 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-18203 are linked in the Vendor Advisories panel on this page.

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