Vulnerability-Lookup

CVE-2026-9803 (GCVE-0-2026-9803)

Vulnerability from cvelistv5 – Published: 2026-05-28 04:47 – Updated: 2026-06-26 06:46

Title

Keycloak: keycloak: denial of service via malformed authorization header

Summary

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.

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-28 13:09 UTC

CWE

CWE-125 - Out-of-bounds Read

Assigner

redhat redhat root

References

6 references

URL	Tags
https://access.redhat.com/errata/RHSA-2026:25097	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:25098	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:30049	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:30050	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/security/cve/CVE-2026-9803	vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2482465	issue-trackingx_refsource_REDHAT

Impacted products

6 products

Vendor	Product	Version
Red Hat	Red Hat build of Keycloak 26.4	Unaffected: 26.4.13-1 , < * (rpm) cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat	Red Hat build of Keycloak 26.4	Unaffected: 26.4-19 , < * (rpm) cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat	Red Hat build of Keycloak 26.4.13	cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat	Red Hat build of Keycloak 26.6	Unaffected: 26.6.3-3 , < * (rpm) cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat	Red Hat build of Keycloak 26.6	Unaffected: 26.6-6 , < * (rpm) cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat	Red Hat build of Keycloak 26.6.3	cpe:/a:redhat:build_keycloak:26.6::el9

Date Public

2026-05-28 04:03

Credits

Red Hat would like to thank Mustafa Çetin for reporting this issue.

Show details on NVD website

JSON

To clipboard

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}

FKIE_CVE-2026-9803

Vulnerability from fkie_nvd - Published: 2026-05-28 06:16 - Updated: 2026-06-26 08:16

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Summary

References

URL	Tags
secalert@redhat.com	https://access.redhat.com/errata/RHSA-2026:25097
secalert@redhat.com	https://access.redhat.com/errata/RHSA-2026:25098
secalert@redhat.com	https://access.redhat.com/errata/RHSA-2026:30049
secalert@redhat.com	https://access.redhat.com/errata/RHSA-2026:30050
secalert@redhat.com	https://access.redhat.com/security/cve/CVE-2026-9803	Vendor Advisory
secalert@redhat.com	https://bugzilla.redhat.com/show_bug.cgi?id=2482465	Issue Tracking, Vendor Advisory

Impacted products

	Vendor	Product	Version
	redhat	build_of_keycloak	-

JSON

To clipboard

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  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://catalog.redhat.com/software/containers/",
          "cpes": [
            "cpe:/a:redhat:build_keycloak:26.4::el9"
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  "lastModified": "2026-06-26T08:16:35.157",
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      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
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            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-05-28T13:09:44.442993Z",
          "version": "2.0.3"
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      }
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  "published": "2026-05-28T06:16:29.750",
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  "sourceIdentifier": "secalert@redhat.com",
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "description": [
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          "lang": "en",
          "value": "CWE-125"
        }
      ],
      "source": "secalert@redhat.com",
      "type": "Secondary"
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  ]
}

GHSA-CPF7-J4CF-VQX4

Vulnerability from github – Published: 2026-05-28 06:31 – Updated: 2026-07-01 21:27

Summary

Keycloak has an Out-of-bounds Read

Details

Severity

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.keycloak:keycloak-services"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "26.4.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.keycloak:keycloak-services"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "26.5.0"
            },
            {
              "fixed": "26.6.3"
            }
          ],
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        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-9803"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-125"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-01T21:27:37Z",
    "nvd_published_at": "2026-05-28T06:16:29Z",
    "severity": "MODERATE"
  },
  "details": "A flaw was found in Keycloak\u0027s ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed \u0027Authorization: Bearer\u0027 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.",
  "id": "GHSA-cpf7-j4cf-vqx4",
  "modified": "2026-07-01T21:27:37Z",
  "published": "2026-05-28T06:31:10Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9803"
    },
    {
      "type": "WEB",
      "url": "https://github.com/keycloak/keycloak/issues/49433"
    },
    {
      "type": "WEB",
      "url": "https://github.com/keycloak/keycloak/pull/49500"
    },
    {
      "type": "WEB",
      "url": "https://github.com/keycloak/keycloak/pull/49617"
    },
    {
      "type": "WEB",
      "url": "https://github.com/keycloak/keycloak/pull/49618"
    },
    {
      "type": "WEB",
      "url": "https://github.com/keycloak/keycloak/commit/2b8692499e907e6205be0bd9c8a4da5d46f6ca30"
    },
    {
      "type": "WEB",
      "url": "https://github.com/keycloak/keycloak/commit/3fc06909cc93eb5c4739a712fa350de625812e04"
    },
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      "type": "WEB",
      "url": "https://github.com/keycloak/keycloak/commit/ef06df91d344c7e99fcb82987ef6adb854f30789"
    },
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    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:25098"
    },
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      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:30049"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:30050"
    },
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      "type": "WEB",
      "url": "https://access.redhat.com/security/cve/CVE-2026-9803"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2482465"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/keycloak/keycloak"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
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  "summary": "Keycloak has an Out-of-bounds Read"
}

RHSA-2026:25097

Vulnerability from csaf_redhat - Published: 2026-06-10 17:35 - Updated: 2026-08-04 10:44

Summary

Red Hat Security Advisory: Red Hat build of Keycloak 26.6.3 Images Update

Severity

Moderate

Scope

14 vulnerabilities in this advisory, including CVE-2026-9803.

CVE-2026-9803

5.3 (Medium)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Fixed: 9 products

https://access.redhat.com/errata/RHSA-2026:25097

Open the full advisory

RHSA-2026:25098

Vulnerability from csaf_redhat - Published: 2026-06-10 17:38 - Updated: 2026-08-27 01:55

Summary

Red Hat Security Advisory: Red Hat build of Keycloak 26.6.3 Update

Severity

Moderate

Scope

14 vulnerabilities in this advisory, including CVE-2026-9803.

CVE-2026-9803

5.3 (Medium)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Fixed: 1 product

https://access.redhat.com/errata/RHSA-2026:25098

Open the full advisory

RHSA-2026:30049

Vulnerability from csaf_redhat - Published: 2026-06-25 17:36 - Updated: 2026-09-13 00:09

Summary

Red Hat Security Advisory: Red Hat build of Keycloak 26.4.13 Security Update

Severity

Important

Scope

22 vulnerabilities in this advisory, including CVE-2026-9803.

CVE-2026-9803

5.3 (Medium)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Fixed: 1 product

https://access.redhat.com/errata/RHSA-2026:30049

Open the full advisory

RHSA-2026:30050

Vulnerability from csaf_redhat - Published: 2026-06-25 17:40 - Updated: 2026-09-13 00:09

Summary

Red Hat Security Advisory: Red Hat build of Keycloak 26.4.13 Images Security Update

Severity

Important

Scope

22 vulnerabilities in this advisory, including CVE-2026-9803.

CVE-2026-9803

5.3 (Medium)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Fixed: 9 products

https://access.redhat.com/errata/RHSA-2026:30050

Open the full advisory

WID-SEC-W-2026-1708

Vulnerability from csaf_certbund - Published: 2026-05-27 22:00 - Updated: 2026-06-10 22:00

Summary

Keycloak: Mehrere Schwachstellen

Severity

Mittel

Scope

12 vulnerabilities in this advisory, including CVE-2026-9803.

CVE-2026-9803

Known affected: 3 products

Open the full advisory

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-9803 (GCVE-0-2026-9803)

FKIE_CVE-2026-9803

GHSA-CPF7-J4CF-VQX4

RHSA-2026:25097

RHSA-2026:25098

RHSA-2026:30049

RHSA-2026:30050

WID-SEC-W-2026-1708

Tags

Sightings

Nomenclature