CVE-2026-73421: Auth.js: Configuration errors can cause existence-based auth checks to fail open (auth object populated with an error)

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.6%, percentile 50: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 50% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes next-auth (npm) >= 5.0.0-beta.0, <= 5.0.0-beta.31, fixed in 5.0.0-beta.32. Check your lockfile, including transitive dependencies.

What it is

NextAuth.js provides authentication for Next.js. From next-auth 5.0.0-beta.0 until 5.0.0-beta.32, applications that gate access by checking only for the existence of the auth object returned by the auth() wrapper can fail open when Auth.js has a server configuration error. In middleware, Route Handlers, React Server Components, and other auth() entry points, a non-OK session response is parsed into a truthy error object instead of null, so checks such as !!auth and if (req.auth) evaluate to true for unauthenticated requests. A provider missing both the issuer and authorization endpoint triggers InvalidEndpoints, and an unset AUTHSECRET or another server configuration error can produce the same behavior. There is no impact while configuration is valid, but after a deployment becomes misconfigured, routes protected only by session existence silently grant access to every visitor. This issue is fixed in next-auth 5.0.0-beta.32.

From the GitHub advisory

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:

Weakness type: CWE-285, CWE-636.

Product: next-auth (npm) · Assigned by: GitHub_M · Published: 2026-08-13

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: present (depends on deployment conditions)
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.64% probability of exploitation activity in the next 30 days; percentile 50.

Timeline

• 2026-07-23 — GitHub-reviewed advisory GHSA-8fpg-xm3f-6cx3 published (critical)
• 2026-08-13 — CVE record published by GitHub_M
• 2026-08-18 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-8fpg-xm3f-6cx3 github.com
2. CVE.org record CVE-2026-73421 cve.org
3. NVD entry CVE-2026-73421 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

Critical npm advisories · Today’s Security Digest