CVE-2026-57817: Apache CXF: The authorization code hash (c_hash) is not enforced for the hybrid OIDC flow

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-06 · updated 2026-10-24
Weakness: CWE-20

Description

The OpenID Connect Core 1.0 specification mandates that the RP MUST validate the `c_hash` parameter when operating in the Hybrid Flow. If an Apache CXF RP is integrated with a non-compliant or misconfigured Identity Provider (IdP) that omits the `c_hash`, the RP becomes vulnerable to Authorization Code Substitution/Injection attacks. Users are recommended to upgrade to versions 4.2.3 or 4.1.8 or 3.6.12, which fix this issue.

Affected products

Apache Software Foundation Apache CXF: before 3.6.12; from 4.0.0 before 4.1.8; from 4.2.0 before 4.2.3 — fixed in 3.6.12, 4.1.8, 4.2.3

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache CXF 3.6.12, 4.1.8, 4.2.3. Check the vendor advisory for mitigations.

References

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