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GHSA-vrh8-c9cm-wh8v
github.com/zitadel/zitadelSummary
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:
4.0.0through4.15.2(including RC versions) - 3.x:
3.0.0through3.4.12(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.
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 (
ZITADEL_DEFAULTINSTANCE_FEATURES_TOKENEXCHANGE=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.
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The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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