ZITADEL is an open source identity management platform. Prior to 3.4.12 and 4.15.2, ZITADEL's external JWT Identity Provider validation in internal/idp/providers/jwt/session.go skips the maximum token age freshness check when an incoming token omits the iat claim, allowing arbitrarily old tokens from a trusted issuer to pass authentication. This issue is fixed in versions 3.4.12 and 4.15.2.

Affected: Go: github.com/zitadel/zitadel

### Summary

A token lifecycle validation vulnerability was discovered in ZITADEL's external JWT Identity Provider (IdP) implementation. ZITADEL enforces a 1-hour maximum token age freshness window (`maxAge`) calculated from the token's issue time. However, this safety check is guarded by a presence condition. If an incoming token omits the `iat` claim, the freshness check is entirely bypassed, allowing arbitrarily old tokens to pass authentication successfully.

Per the OIDC Core 1.0 specification, identity token validation pipelines must strictly handle and enforce session expiration. ZITADEL's silent acceptance of tokens missing these temporal constraints compromises session integrity.

### Impact

An attacker in possession of a stale token lacking an `iat` claim can reuse it indefinitely without triggering the maximum age freshness invalidation.

### Affected Versions

Systems running one of the following versions are affected:

* **4.x**: `4.0.0` through `4.15.1` (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. ZITADEL now explicitly rejects tokens that lack an `iat` claim.

* **4.x**: Upgrade to $\ge$ [4.15.2](https://github.com/zitadel/zitadel/releases/tag/v4.15.2) * **3.x**: Upgrade to $\ge$ [3.4.12](https://github.com/zitadel/zitadel/releases/tag/v3.4.12)

### Workarounds

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

If an immediate u…