CVE-2026-9803

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

Score 5.3 from GitHub Security Advisory published 2026-05-28. a secondary CVSS source baseline 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.3Exploit: NoneExposed: 0

A fix is available — apply it.

A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service.

CVSS v3
5.3
EG Score
5.3(medium)
EPSS
34.1%
KEV
Not listed

Published

May 28, 2026

Last Modified

June 26, 2026

Advisory Details (4)

Auto-updated Jun 16, 2026
Patch available. Sources: redhat.
redhat

2482465 – (CVE-2026-9803) CVE-2026-9803 keycloak: Keycloak: Denial of Service via malformed Authorization header

https://bugzilla.redhat.com/show_bug.cgi?id=2482465
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-9803
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:25098
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:25097

Vendor Advisories for CVE-2026-9803(5)

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

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatrhbk/keycloak-rhel9-operator:26.4-192026-06-25redhat
redhatrhbk/keycloak-rhel92026-06-25redhat
redhatrhbk/keycloak-rhel9-operator:26.6-62026-06-10redhat

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.

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.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-9803?
CVE-2026-9803 is a medium vulnerability published on May 28, 2026. A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an…
When was CVE-2026-9803 disclosed?
CVE-2026-9803 was first published in the National Vulnerability Database on May 28, 2026, with the most recent update on June 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-9803 actively exploited?
CVE-2026-9803 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 34.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-9803?
CVE-2026-9803 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-9803?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-9803, 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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