CVE-2026-18209

MEDIUMNVD 4.74.7—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.7 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 86% of all CVEs by exploit prediction. GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
Trending — Patch released this week
4.7EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 4.7Exploit: None knownExposed: 0

A fix is available — apply it.

A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect (OIDC) authentication flows. The issue occurs because the security check designed to prevent HTTP parameter pollution only inspects the query portion of a redirect URL and ignores the fragment portion. When a client is configured with a wildcard redirect URI, an attacker can use this to inject duplicate security parameters into the login response. If a client application is not configured correctly, it might trust the attacker's injected data instead of the real security information from Keycloak, leading to session fixation or account confusion.

CVSS v3
4.7
EG Score
4.7(medium)
EG Risk
21(Track)
EG Risk 21/100SSVC: 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
Severity47% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
14%
KEV
Not listed

Published

July 31, 2026

Last Modified

September 16, 2026

Advisory Details (2)

Auto-updated Aug 7, 2026
Patch available. Sources: redhat.
redhat

2508305 – (CVE-2026-18209) CVE-2026-18209 keycloak-services: keycloak-services: OIDC redirect_uri fragment bypass in HTTP parameter pollution check

https://bugzilla.redhat.com/show_bug.cgi?id=2508305
redhat Patch Available

CVE-2026-18209 - Red Hat Customer Portal

Affected: Red Hat Enterprise Linux 8 or OpenShift Container Platform 4, is affected by this vulnerability and a fix may be released to a

https://access.redhat.com/security/cve/CVE-2026-18209

Vendor Advisories for CVE-2026-18209(2)

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

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatrhbk-openshift-rhel9/rhbk-openshift-rhel92026-09-16redhat
redhatrhbk/keycloak-rhel9-operator:26.6-202026-09-16redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 23× in last 7d / 80× 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 134 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-18209?
CVE-2026-18209 is a medium vulnerability published on July 31, 2026. A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect (OIDC) authentication flows. The issue occurs because the security check designed to prevent HTTP parameter pollution only inspects the query portion of a redirect URL and ignores the fragment portion.…
When was CVE-2026-18209 disclosed?
CVE-2026-18209 was first published in the National Vulnerability Database on July 31, 2026, with the most recent update on September 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-18209 actively exploited?
CVE-2026-18209 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 85.7% of all scored CVEs.
What is the CVSS score of CVE-2026-18209?
CVE-2026-18209 has a CVSS v3 base score of 4.7 (NVD).
How do I remediate CVE-2026-18209?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-18209, 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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