Summary
ZITADEL: Cross-Tenant User Leakage via Recycled Identifiers
A flaw in the user lifecycle enforcement allowed deleted users to retain their original organization/tenant association. Recreating a deleted user under a distinct organization can cause the new user instance to be incorrectly provisioned within the original organization if the previous ID would be used to recreate it.
Affected Versions
Systems running one of the following versions are affected:
- 4.x:
4.0.0through4.15.1(including RC versions) - 3.x:
3.0.0through3.4.11(including RC versions)
Workarounds
The recommended solution is to upgrade to a patched version.
Questions
If you have any questions or comments about this advisory, please email us at [email protected]
Credits
Thanks to Charlie Graven from Famedly for reporting this vulnerability.
Impact
When a user is created, the system maps the generated or provided ID to its target organization (Org A). When that user is subsequently deleted, a deletion event is appended to the stream, but the historical mapping of the resource owner within the event store's validation layer is not cleared.
If a new user is later provisioned in a different organization (Org B) using that exact same ID, the event store validation logic reads the stream's history, matches it to the original organization, and routes the new user's events to Org A instead of Org B.
This issue represents a localized multi-tenancy isolation anomaly rather than an easily exploitable attack vector. Because the new user instance is incorrectly routed and provisioned inside Org A instead of Org B, an administrator from Org A inadvertently gains full access to this new user record.
However, there is no technical mechanism for a malicious actor to force, automate, or target this behavior against a specific user or tenant. Because the scenario relies entirely on an accidental sequence of operational events and requires the recycling of a highly specific ID space, the practical security risk is exceptionally low.
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 requiring the correct permission in case the verification flag is provided and only allows self-management of the email address, resp. phone number itself.
Frequently Asked Questions
- What is CVE-2026-55670? CVE-2026-55670 is a low-severity security vulnerability in github.com/zitadel/zitadel (go), affecting versions < 1.80.0-v2.20.0.20260615092437-6082e59d47c1. It is fixed in 1.80.0-v2.20.0.20260615092437-6082e59d47c1.
- Which versions of github.com/zitadel/zitadel are affected by CVE-2026-55670? github.com/zitadel/zitadel (go) versions < 1.80.0-v2.20.0.20260615092437-6082e59d47c1 is affected.
- Is there a fix for CVE-2026-55670? Yes. CVE-2026-55670 is fixed in 1.80.0-v2.20.0.20260615092437-6082e59d47c1. Upgrade to this version or later.
- Is CVE-2026-55670 exploitable, and should I be worried? Whether CVE-2026-55670 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-2026-55670 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-2026-55670? Upgrade
github.com/zitadel/zitadelto 1.80.0-v2.20.0.20260615092437-6082e59d47c1 or later.