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Medium, CVSS 4.8amended

ZITADEL: Auto-linking by email: IdP-side email verification is not checked

CVE-2026-56666GHSA-992q-9gwp-7r79

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/zitadel/zitadel 4.15.3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
4.8 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
EPSS
  • CVE-2026-56666: 0.29% estimated exploitation activity in the next 30 days; percentile 21.13 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary A flaw in the external identity provider handler allows unauthorized account linking to occur under specific administrative configurations. When auto-linking by email is enabled, ZITADEL checks that the local user's email is verified, but does not explicitly cross-check whether the incoming external identity provider (IdP) also verified that email address upstream. Impact When a user logs in via an external identity provider, the system can automatically link them to an existing local account if their email addresses match. However, because the system fails to check if the external provider actually verified ownership of that email, a security risk is introduced if a loose or public provider is connected. If an administrator enables email auto-linking for an external identity provider that allows anyone to sign up with an unverified email address, an attacker can exploit this behavior. By registering an account on that permissive provider using a victim's email address and…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-992q-9gwp-7r79

  2. Revision 2 · amended ·

    Amended from osv record GO-2026-6470

  3. Revision 1 · created ·

    Published from osv record GHSA-992q-9gwp-7r79

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-56666

Advisory: ZITADEL: Auto-linking by email: IdP-side email verification is not checked
IDs: CVE-2026-56666, GHSA-992q-9gwp-7r79
Record: https://patchnext.com/advisories/cve-2026-56666 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/zitadel/zitadel 4.15.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/zitadel/zitadel: affected < 4.15.3; fixed in 4.15.3

## Suggested inspection (read-only)
- Go github.com/zitadel/zitadel: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/zitadel/zitadel.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-992q-9gwp-7r79 (OSV record GHSA-992q-9gwp-7r79 lists affected ranges: Go github.com/zitadel/zitadel >=0 <4.15.3 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6470 (OSV record GO-2026-6470 lists affected ranges: Go github.com/zitadel/zitadel >=0)
- Verified: https://github.com/advisories/GHSA-992q-9gwp-7r79 (GitHub-reviewed advisory GHSA-992q-9gwp-7r79 lists affected ranges: Go github.com/zitadel/zitadel >=0 <4.15.3)

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