Keycloak: keycloak: denial of service via malformed authorization header
Priority LOW 30CWE-125Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00417 36th percentileScored 2026-11-07
Fix Fixed org.keycloak:keycloak-services (Maven): 26.6.3Red Hat: 4 advisories
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Red Hat | Red Hat build of Keycloak 26.4 | — | 26.4.13-1 | Patch available | CNA |
| Red Hat | Red Hat build of Keycloak 26.4 | — | 26.4-19 | Patch available | CNA |
| Red Hat | Red Hat build of Keycloak 26.4 | — | 26.4-19 | Patch available | CNA |
| Red Hat | Red Hat build of Keycloak 26.4.13 | — | — | Not affected | CNA |
| Red Hat | Red Hat build of Keycloak 26.6 | — | 26.6.3-3 | Patch available | CNA |
| Red Hat | Red Hat build of Keycloak 26.6 | — | 26.6-6 | Patch available | CNA |
| Red Hat | Red Hat build of Keycloak 26.6 | — | 26.6-6 | Patch available | CNA |
| Red Hat | Red Hat build of Keycloak 26.6.3 | — | — | Not affected | CNA |
| — | org.keycloak:keycloak-services (Maven) | up to 26.4.7 | — | No fix listed | GHSA-cpf7-j4cf-vqx4 |
| — | org.keycloak:keycloak-services (Maven) | 26.5.0 to before 26.6.3 | 26.6.3 | Patch available | GHSA-cpf7-j4cf-vqx4 |
- Red Hat build of Keycloak 26.4 VendorRed Hat Affected — Fixed in 26.4.13-1 Patch available CNA
- Red Hat build of Keycloak 26.4 VendorRed Hat Affected — Fixed in 26.4-19 Patch available CNA
- Red Hat build of Keycloak 26.4 VendorRed Hat Affected — Fixed in 26.4-19 Patch available CNA
- Red Hat build of Keycloak 26.4.13 VendorRed Hat Affected — Fixed in — Not affected CNA
- Red Hat build of Keycloak 26.6 VendorRed Hat Affected — Fixed in 26.6.3-3 Patch available CNA
- Red Hat build of Keycloak 26.6 VendorRed Hat Affected — Fixed in 26.6-6 Patch available CNA
- Red Hat build of Keycloak 26.6 VendorRed Hat Affected — Fixed in 26.6-6 Patch available CNA
- Red Hat build of Keycloak 26.6.3 VendorRed Hat Affected — Fixed in — Not affected CNA
- org.keycloak:keycloak-services (Maven) Vendor— Affected up to 26.4.7 Fixed in — No fix listed GHSA-cpf7-j4cf-vqx4
- org.keycloak:keycloak-services (Maven) Vendor— Affected 26.5.0 to before 26.6.3 Fixed in 26.6.3 Patch available GHSA-cpf7-j4cf-vqx4
Remediation
- Fix · GHSA-cpf7-j4cf-vqx4 org.keycloak:keycloak-services (Maven) Fixed in 26.6.3 Advisory →
Red Hat 4 advisories
- RHSA-2026:30050 Released 2026-06-25 · Red Hat rating ImportantRed Hat build of Keycloak 26.4.13 Images Security Update
- Red Hat build of Keycloak 26.4 rhbk/keycloak-operator-bundle, rhbk/keycloak-rhel9, rhbk/keycloak-rhel9-operator
- RHSA-2026:30049 Released 2026-06-25 · Red Hat rating ImportantRed Hat build of Keycloak 26.4.13 Security Update
- Red Hat build of Keycloak 26.4.13
- RHSA-2026:25098 Released 2026-06-10 · Red Hat rating ModerateRed Hat build of Keycloak 26.6.3 Update
- Red Hat build of Keycloak 26.6.3
Show 1 more Red Hat advisories
- RHSA-2026:25097 Released 2026-06-10 · Red Hat rating ModerateRed Hat build of Keycloak 26.6.3 Images Update
- Red Hat build of Keycloak 26.6 rhbk/keycloak-operator-bundle, rhbk/keycloak-rhel9, rhbk/keycloak-rhel9-operator
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat build of Keycloak 26.4 | Fixed | RHSA-2026:30050 |
| Red Hat build of Keycloak 26.4.13 | Fixed | RHSA-2026:30049 |
| Red Hat build of Keycloak 26.6 | Fixed | RHSA-2026:25097 |
| Red Hat build of Keycloak 26.6.3 | Fixed | RHSA-2026:25098 |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-9803
- 2026-10-03 Alias added: GHSA-cpf7-j4cf-vqx4
- 2026-10-25 EPSS moved to the below the 50th percentile
References
Advisory 7
Other 8
- https://github.com/keycloak/keycloak/issues/49433
- https://github.com/keycloak/keycloak/pull/49500
- https://github.com/keycloak/keycloak/pull/49617
- https://github.com/keycloak/keycloak/pull/49618
- https://github.com/keycloak/keycloak/commit/2b8692499e907e6205be0bd9c8a4da5d46f6ca30
- https://github.com/keycloak/keycloak/commit/3fc06909cc93eb5c4739a712fa350de625812e04
- https://github.com/keycloak/keycloak/commit/ef06df91d344c7e99fcb82987ef6adb854f30789
- https://github.com/keycloak/keycloak
More Red Hat Build Of Keycloak vulnerabilities
- TI-2026-02223 Keycloak: keycloak: unauthorized authentication via disabled saml identity provider CVSS 3.1HIGH 8.1
- TI-2024-01049 Keycloak: path transversal in redirection validation CVSS 3.1HIGH 8.1
- TI-2026-13740 Keycloak-services: keycloak-services: saml idp-initiated broker login bypasses link-only restriction CVSS 3.1CRITICAL 9.8
- TI-2026-13741 Keycloak-services: keycloak-services: saml broker metadata import disables response signature validation CVSS 3.1CRITICAL 9.1
- TI-2026-13106 Keycloak-services: keycloak-services: dcr protocol mapper type-swap policy bypass allows privilege escalation CVSS 3.1HIGH 8.8
- TI-2026-02631 Authentication bypass in Red Hat build of Keycloak 26.2 CVSS 3.1HIGH 8.8
Sources
- CVE-2026-9803 · CVE Program
- CVE-2026-9803 · NVD
- FIRST EPSS
- GHSA-cpf7-j4cf-vqx4 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-9803 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences