How severe is CVE-2026-55670?

No CVSS score has been assigned to CVE-2026-55670 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-55670?

CVE-2026-55670 affects the following packages: github.com/zitadel/zitadel (Go). Ecosystems affected: Go.

How do I fix CVE-2026-55670?

Update github.com/zitadel/zitadel to 1.80.0-v2.20.0.20260615092437-6082e59d47c1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55670 is resolved across your whole dependency graph.

How do I detect CVE-2026-55670 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/zitadel/zitadel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-55670 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-55670 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-55670 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-55670?

CVE-2026-55670 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 30th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-55670?

CVE-2026-55670 is classified as CWE-284 (CWE-284), CWE-639 (CWE-639). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-55670 published, and has it been updated?

CVE-2026-55670 was published on July 10, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2026-55670 — zitadel

Fix: zitadel/zitadel@a939b84

CVE-2026-55670 is a CWE-284 vulnerability in github.com/zitadel/zitadel. A fix is available for github.com/zitadel/zitadel — see the affected versions and patch details below.

ZITADEL: Cross-Tenant User Leakage via Recycled Identifiers

Also known asGHSA-6x8v-2fq5-2229GO-2026-5197

Published

Jul 10, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55670.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs30th percentile — riskier than 30% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹github.com/zitadel/zitadel

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

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.

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

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. 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.

4.x: Upgrade to $\ge$4.15.2
3.x: Update to $\ge$4.15.2

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/zitadel/zitadel`	all versions	1.80.0-v2.20.0.20260615092437-6082e59d47c1`go get github.com/zitadel/zitadel@v1.80.0-v2.20.0.20260615092437-6082e59d47c1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/zitadel/zitadel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/zitadel/zitadel to 1.80.0-v2.20.0.20260615092437-6082e59d47c1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55670 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### Summary 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. ### 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 ev

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