ZITADEL: Missing client_id binding in OIDC authorization code exchange and refresh token flows (RFC 6749 Section 4.1.3 violation)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.4 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-55672: 0.43% estimated exploitation activity in the next 30 days; percentile 37.64 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Zitadel's OAuth2 / OIDC CodeExchange and RefreshToken implementations omit a critical validation step to ensure that the requesting client matches the client that originally initiated the authorization flow. This violates RFC 6749 Section 4.1.3, which mandates that the authorization server must ensure the authorization code was issued to the authenticated confidential client. Impact This flaw creates potential vulnerabilities in two main authentication phases, provided specific external preconditions are met: Authorization Code Injection: An attacker who intercepts an authorization code (via an independent application vulnerability such as XSS, referrer leakage, log access, or network interception) can exchange it using credentials from a completely different client (ClientB) registered on the same Zitadel instance. Zitadel will authenticate ClientB and issue tokens for the victim user without verifying the client binding. Refresh Token Cross-Use: An attacker who successfully…

Published by the source

18 Jun 2026, 13:52 UTC

Last modified by the source

15 Jul 2026, 21:51 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xqxv-4jc2-x56x

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# Patch Next advisory brief: CVE-2026-55672

Advisory: ZITADEL: Missing client_id binding in OIDC authorization code exchange and refresh token flows (RFC 6749 Section 4.1.3 violation)
IDs: CVE-2026-55672, GHSA-xqxv-4jc2-x56x
Record: https://patchnext.com/advisories/cve-2026-55672 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/zitadel/zitadel 1.80.0-v2.20.0.20260616131956-0973b074b488. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/zitadel/zitadel: affected < 1.80.0-v2.20.0.20260616131956-0973b074b488; fixed in 1.80.0-v2.20.0.20260616131956-0973b074b488

## Suggested inspection (read-only)
- Go github.com/zitadel/zitadel: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/zitadel/zitadel.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-xqxv-4jc2-x56x (GitHub-reviewed advisory GHSA-xqxv-4jc2-x56x lists affected ranges: Go github.com/zitadel/zitadel >=0 <1.80.0-v2.20.0.20260616131956-0973b074b488)

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