GHSA-vrh8-c9cm-wh8v: High severity go/github.com/zitadel/zitadel vulnerability
Summary
A vulnerability in ZITADEL’s OAuth2 Token Exchange endpoint allows an authenticated user or client to exchange a low-privilege access token for a token with elevated permissions at a completely different application. This bypasses the intended authorization and separation policies configured within ZITADEL.
Impact
ZITADEL enables administrators to restrict token issuance based on client permissions, project roles, and specific scopes. Due to a missing verification step during the Token Exchange flow (urn:ietf:params:oauth:grant-type:token-exchange), ZITADEL fails to validate whether the incoming access token belongs to or is authorized for the client initiating the exchange. Additionally, ZITADEL does not enforce that the newly requested scopes must stay within the boundaries of the original token's scopes.
An attacker with valid access to a low-privilege application can exploit this behavior by sending a token exchange request to a highly-privileged target application. This allows them to obtain administrative project roles, access sensitive profile data, or gain unauthorized access to other applications across the system. If public clients (which do not require client secrets) are used, this risk increases significantly as it requires no client authentication.
Affected Versions
Systems running one of the following versions are affected:
4.x: 4.0.0 through 4.15.2 (including RC versions) 3.x: 3.0.0 through 3.4.12 (including RC versions)
Patches
The vulnerability has been addressed in the latest releases. The patch resolves the issue by enforcing strict audience ownership verification and ensuring that requested scopes during a token exchange are restricted to a subset of the original token’s scopes.
4.x: Upgrade to $\ge$ 4.15.3 3.x: Upgrade to $\ge$ 4.15.3
Workarounds
The recommended solution is to upgrade to a patched version immediately. If an immediate upgrade is not possible, implement one of the following mitigations: - Disable via Feature Flag: Ensure the Token Exchange feature flag is explicitly turned off in your instance settings or environment variables (ZITADELDEFAULTINSTANCEFEATURESTOKENEXCHANGE=false). If the feature flag is disabled, the endpoint is unreachable and your system is not vulnerable. This is only possible in versions prior to v4.11.0, where the feature was not yet GA. - Remove the Grant Type: Ensure that the Token Exchange grant type is completely disabled or removed from all configured applications—especially high-privilege or public clients.
Questions
If you have any questions or comments about this advisory, please email us at security@zitadel.com.
Credits
Thanks to thesecguy45 and Shubham Raj / Causal Security for reporting this vulnerability.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/zitadel/zitadelto a version that resolves this vulnerability.Fixed in 4.15.3 - Upgrade
Upgrade
zitadelto a version that resolves this vulnerability.Fixed in 4.15.3 - Configuration
Disable the Token Exchange feature flag so the OAuth2 Token Exchange endpoint is unreachable (set ZITADEL_DEFAULTINSTANCE_FEATURES_TOKENEXCHANGE=false in your instance settings/environment variables).
ZITADEL instance feature flags ZITADEL_DEFAULTINSTANCE_FEATURES_TOKENEXCHANGE = false - Configuration
Remove/disable the Token Exchange grant type from all configured applications, especially high-privilege or public clients, so token exchange requests cannot be initiated.
ZITADEL OAuth2 applications Token Exchange grant type = disabled/removed
Event History
Frequently Asked Questions
Who can exploit this issue?
An attacker needs a valid access token from a low-privilege application and must be able to submit an OAuth 2.0 Token Exchange request. Public clients are especially relevant because they do not require client authentication, although the provided information is incomplete after that point.
What authorization controls does the vulnerable token exchange bypass?
The endpoint does not verify that the supplied access token belongs to, or is authorized for, the client requesting the exchange. It also allows requested scopes outside the original token’s scope boundaries, potentially enabling tokens for a more privileged application or project role.
What could an attacker obtain through successful exploitation?
An attacker may obtain elevated permissions at a different application, including administrative project roles, access to sensitive profile data, or unauthorized access to other applications in the same system.