Auth.js: Configuration errors can cause existence-based auth checks to fail open (auth object populated with an error)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

9.1 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-73421: 0.64% estimated exploitation activity in the next 30 days; percentile 50.87 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact next-auth (Auth.js) v5 applications that gate access by checking only for the existence of the auth object — the pattern shown in the official session management / protecting resources guide — are affected. When the Auth.js configuration produces a server-side error, the auth object exposed by the auth() wrapper (in middleware, Route Handlers, etc.) is populated with an error object instead of being null: Because this object is truthy, any authorization check of the form !!auth (or if (req.auth)) evaluates to true for every request, including unauthenticated ones. The application fails open: instead of denying access when the auth layer is broken, it grants access to everyone. A representative trigger is a provider that is missing required configuration. For example, a Keycloak provider with neither issuer nor authorization endpoint set logs: …and from that point on auth is the error object above, so !!auth is permanently true. The same fail-open behavior occurs for other…

Published by the source

23 Jul 2026, 14:52 UTC

Last modified by the source

12 Aug 2026, 20:56 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-8fpg-xm3f-6cx3

2. Revision 3 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-8fpg-xm3f-6cx3

4. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-8fpg-xm3f-6cx3

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# Patch Next advisory brief: CVE-2026-73421

Advisory: Auth.js: Configuration errors can cause existence-based auth checks to fail open (auth object populated with an error)
IDs: CVE-2026-73421, GHSA-8fpg-xm3f-6cx3
Record: https://patchnext.com/advisories/cve-2026-73421 (revision 4, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: next-auth 5.0.0-beta.32. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm next-auth: affected >= 5.0.0-beta.0, <= 5.0.0-beta.31; fixed in 5.0.0-beta.32

## Suggested inspection (read-only)
- `npm ls next-auth --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## 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 next-auth.
- 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://github.com/advisories/GHSA-8fpg-xm3f-6cx3 (GitHub-reviewed advisory GHSA-8fpg-xm3f-6cx3 lists affected ranges: npm next-auth >=5.0.0-beta.0 <=5.0.0-beta.31)
- Verified: https://osv.dev/vulnerability/GHSA-8fpg-xm3f-6cx3 (OSV record GHSA-8fpg-xm3f-6cx3 lists affected ranges: npm next-auth >=5.0.0-beta.0 <5.0.0-beta.32 (fixed))

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