CVE-2026-18203

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory published 2026-07-31. a secondary CVSS source baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
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%CVSS: 6.5Exploit: None knownExposed: 0

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

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
6.5(high)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
8%
KEV
Not listed

Published

July 31, 2026

Last Modified

August 7, 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 21× in last 7d / 66× 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.

  1. 2026-08-21 04:53 UTCGHSA enrichment
  2. 2026-08-20 05:39 UTCEG score recompute
  3. 2026-08-20 05:39 UTCGHSA enrichment
  4. 2026-08-19 17:03 UTCEPSS rescore
  5. 2026-08-19 06:25 UTCEG score recompute
  6. 2026-08-19 06:24 UTCGHSA enrichment
  7. 2026-08-18 13:48 UTCEPSS rescore
  8. 2026-08-18 06:50 UTCEG score recompute
  9. 2026-08-18 06:50 UTCGHSA enrichment
  10. 2026-08-17 13:47 UTCEPSS rescore
  11. 2026-08-17 07:30 UTCEG score recompute
  12. 2026-08-17 07:30 UTCGHSA enrichment
  13. 2026-08-16 14:56 UTCEPSS rescore
  14. 2026-08-16 08:16 UTCEG score recompute
  15. 2026-08-16 08:16 UTCGHSA enrichment
  16. 2026-08-16 02:14 UTCEPSS rescore
  17. 2026-08-15 09:02 UTCEG score recompute
  18. 2026-08-15 09:02 UTCGHSA enrichment
  19. 2026-08-15 01:30 UTCEPSS rescore
  20. 2026-08-14 09:48 UTCEG score recompute
  21. 2026-08-14 09:48 UTCGHSA enrichment
  22. 2026-08-13 22:00 UTCEPSS rescore
  23. 2026-08-13 10:34 UTCEG score recompute
  24. 2026-08-13 10:33 UTCGHSA enrichment
  25. 2026-08-12 13:50 UTCEPSS rescore
Show 41 more
  1. 2026-08-12 11:19 UTCEG score recompute
  2. 2026-08-12 11:19 UTCGHSA enrichment
  3. 2026-08-11 13:42 UTCEPSS rescore
  4. 2026-08-11 12:05 UTCEG score recompute
  5. 2026-08-11 12:05 UTCGHSA enrichment
  6. 2026-08-11 00:00 UTCEPSS rescore
  7. 2026-08-10 12:50 UTCEG score recompute
  8. 2026-08-10 12:50 UTCGHSA enrichment
  9. 2026-08-09 13:46 UTCEPSS rescore
  10. 2026-08-09 13:36 UTCEG score recompute
  11. 2026-08-09 13:36 UTCGHSA enrichment
  12. 2026-08-08 16:37 UTCEPSS rescore
  13. 2026-08-08 14:22 UTCEG score recompute
  14. 2026-08-08 14:22 UTCGHSA enrichment
  15. 2026-08-07 15:07 UTCGHSA enrichment
  16. 2026-08-07 13:52 UTCGHSA enrichment
  17. 2026-08-06 14:39 UTCEG score recompute
  18. 2026-08-06 14:39 UTCGHSA enrichment
  19. 2026-08-06 13:46 UTCEPSS rescore
  20. 2026-08-05 19:17 UTCEPSS rescore
  21. 2026-08-05 15:24 UTCGHSA enrichment
  22. 2026-08-04 16:10 UTCEG score recompute
  23. 2026-08-04 16:10 UTCGHSA enrichment
  24. 2026-08-04 15:10 UTCEPSS rescore
  25. 2026-08-04 10:38 UTCEPSS rescore
  26. 2026-08-03 16:56 UTCEG score recompute
  27. 2026-08-03 16:56 UTCGHSA enrichment
  28. 2026-08-03 10:35 UTCEPSS rescore
  29. 2026-08-02 23:02 UTCEG score recompute
  30. 2026-08-02 23:02 UTCGHSA enrichment
  31. 2026-08-02 02:26 UTCEPSS rescore
  32. 2026-08-01 23:48 UTCEG score recompute
  33. 2026-08-01 23:48 UTCGHSA enrichment
  34. 2026-08-01 04:15 UTCEPSS rescore
  35. 2026-08-01 00:33 UTCEG score recompute
  36. 2026-08-01 00:33 UTCGHSA enrichment
  37. 2026-07-31 23:40 UTCEG score recompute
  38. 2026-07-31 23:40 UTCGHSA enrichment
  39. 2026-07-31 08:18 UTCEG score recompute
  40. 2026-07-31 07:28 UTCEG score recompute
  41. 2026-07-31 07:28 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

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 in the National Vulnerability Database on July 31, 2026, with the most recent update on August 7, 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% probability of exploitation in the next 30 days, which ranks it in the top 91.9% of all scored CVEs.
What is the CVSS score of CVE-2026-18203?
CVE-2026-18203 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-18203?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-18203, 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

Explore the affected products and dependency analysis for CVE-2026-18203

Explore →

Is Your Infrastructure Affected by CVE-2026-18203?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs