Summary
ZITADEL: Unauthorized Token Privilege Escalation in OAuth2 Token Exchange
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.
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)
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 [email protected].
Credits
Thanks to thesecguy45 and Shubham Raj / Causal Security for reporting this vulnerability.
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.
The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.
CVE-2026-56668 has a CVSS score of 8.1 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.15.3); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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.
Frequently Asked Questions
- What is CVE-2026-56668? CVE-2026-56668 is a high-severity missing authorization vulnerability in github.com/zitadel/zitadel (go), affecting versions < 4.15.3. It is fixed in 4.15.3. The application does not perform an authorization check before performing a sensitive operation.
- How severe is CVE-2026-56668? CVE-2026-56668 has a CVSS score of 8.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/zitadel/zitadel are affected by CVE-2026-56668? github.com/zitadel/zitadel (go) versions < 4.15.3 is affected.
- Is there a fix for CVE-2026-56668? Yes. CVE-2026-56668 is fixed in 4.15.3. Upgrade to this version or later.
- Is CVE-2026-56668 exploitable, and should I be worried? Whether CVE-2026-56668 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-56668 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-56668? Upgrade
github.com/zitadel/zitadelto 4.15.3 or later.