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
5.3EG
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

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)
EG Risk
39(Track)
EG Risk 39/100SSVC: 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%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
35%
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.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.keycloak:keycloak-services26.5.0 ... 26.6.2 (11 versions)26.6.3—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 6× in last 7d / 57× 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 185 total refreshes for this CVE.

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

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 0% probability of exploitation in the next 30 days, which ranks it in the top 65.1% of all scored CVEs.
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.

Dependency Blast Radius

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