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MEDIUM severity

ZITADEL: Missing Token Audience Validation (`aud`) in JWT IdP ProviderGHSA-g5h5-m4hm-xjrr

MEDIUMFix: zitadel/zitadel@d184e97

GHSA-g5h5-m4hm-xjrr is a medium-severity (CVSS 4.2) CWE-346 vulnerability in github.com/zitadel/zitadel. A fix is available for github.com/zitadel/zitadel — see the affected versions and patch details below.

Also known asCVE-2026-55669GO-2026-5391
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 28, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-g5h5-m4hm-xjrr.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs5th percentile — riskier than 5% of all scored CVEsHighest risk
0.00%0.22%0.44%0.66%0.1%0.2%0.2%0.2%Aug 26Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-g5h5-m4hm-xjrr by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 397,508 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐹github.com/zitadel/zitadel

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

An authentication bypass vulnerability was discovered in ZITADEL's external JWT Identity Provider (IdP) implementation.

When validating JSON Web Tokens (JWTs) from an external provider, ZITADEL properly checks the token's cryptographic signature and issuer (iss), but it fails to validate the audience (aud) claim.

As a result, any validly signed token from the trusted issuer will be accepted. An attacker who is a legitimate user of a completely separate service sharing the same enterprise Identity Provider can intercept or present their token for that service to ZITADEL, successfully authenticating as that user without authorization.

Impact

In a controlled enterprise environment where Identity Providers are explicitly managed, the operational risk is localized. Exploitation requires that an attacker already possesses a valid standard user session token from a shared, trusted issuer intended for an entirely different relying party, limiting the vector to specific, rare cross-service setups where trust boundaries overlap.

Affected Versions

Systems running one of the following versions are affected:

  • 4.x: 4.0.0 through 4.11.0 (including RC versions)
  • 3.x: 3.0.0 through 3.4.11 (including RC versions)

Patches

The vulnerability has been addressed in the latest releases, where a required audience can be set in the IdP configuration. Once provided, audience validation will be enforced.

Workarounds

The recommended solution is to update ZITADEL to a patched version.

If an immediate upgrade is not possible, you can mitigate the risk at the infrastructure layer:

  1. At the IdP: Ensure the external Identity Provider issues scoped tokens with highly unique, non-overlapping audience values that cannot be misconstrued by separate service deployments.
  2. At the Perimeter: Deploy a reverse proxy, API gateway, or Web Application Firewall (WAF) layer in front of ZITADEL to inspect incoming identity tokens and explicitly drop requests where the aud field does not strictly match ZITADEL's deployment target.

Questions

If you have any questions or comments about this advisory, please email us at [email protected]

Credits

Thanks to Android-Login-Analysis, Jason Zhou and Pedro Giglioti for reporting this vulnerability.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/zitadel/zitadelall versions1.80.0-v2.20.0.20260615132747-d184e976fc79go get github.com/zitadel/zitadel@v1.80.0-v2.20.0.20260615132747-d184e976fc79

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/zitadel/zitadel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/zitadel/zitadel to 1.80.0-v2.20.0.20260615132747-d184e976fc79 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g5h5-m4hm-xjrr is resolved across your whole dependency graph.

  3. Workarounds

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### Summary An authentication bypass vulnerability was discovered in ZITADEL's external JWT Identity Provider (IdP) implementation. When validating JSON Web Tokens (JWTs) from an external provider, ZITADEL properly checks the token's cryptographic signature and issuer (`iss`), but it fails to validate the audience (`aud`) claim. As a result, any validly signed token from the trusted issuer will be accepted. An attacker who is a legitimate user of a completely separate service sharing the same enterprise Identity Provider can intercept or present their token for that service to ZITADEL, succ
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