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CVE-2026-57817 – OpenID Connect Authorization Code Injection (c_hash not enforced) – Apache CXF befo

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Summary

CVE-2026-57817 is an improper input validation vulnerability (CWE-20) in Apache CXF’s OpenID Connect relying-party implementation. The framework fails to enforce validation of the authorization code hash (c_hash) claim required by the OpenID Connect Hybrid Flow, exposing integrations to authorization code substitution/injection attacks. It carries a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: Apache CXF does not enforce validation of the c_hash parameter, which OpenID Connect Core 1.0 requires relying parties to verify during Hybrid Flow.
  • Trigger conditions: Occurs when an Apache CXF relying party is integrated with a non-compliant Identity Provider that omits the c_hash parameter from the ID token.
  • Attack vector: Network-based, requiring no authentication or user interaction.
  • Impact: Enables "Authorization Code Substitution/Injection" attacks, in which an attacker substitutes or injects an authorization code, compromising the confidentiality and integrity of the authentication flow.

Affected software

  • Apache CXF before 3.6.12
  • Apache CXF 4.0.0 through 4.1.7
  • Apache CXF 4.2.0 through 4.2.2

(Affected component: org.apache.cxf:cxf-rt-rs-security-sso-oidc)

Severity

CVSS v3.1 base score: 9.8 (Critical)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade to a fixed release — Apache CXF 3.6.12, 4.1.8, or 4.2.3.
  • If no patch: Ensure any integrated Identity Provider is OpenID Connect compliant and returns the c_hash parameter in the Hybrid Flow, so that code substitution cannot go undetected.

References

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