---
title: "CVE-2026-73421: Auth.js: Configuration errors can cause existence-based auth checks to fail open (auth object populated with an error)"
url: https://erroneo.us/security/cve/CVE-2026-73421/
description: "CVE-2026-73421 (next-auth (npm)): NextAuth.js provides authentication for Next.js. From next-auth 5.0.0-beta.0 until 5.0.0-beta.32, applications that gate…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-08-13
date_modified: 2026-08-18
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-73421"
kev: false
cvss: 9.1
epss: 0.00643
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- 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.

## Affected packages

- npm `next-auth` >= 5.0.0-beta.0, <= 5.0.0-beta.31 → fixed: 5.0.0-beta.32

## Affected products (CVE record)

- nextauthjs next-auth: >= 5.0.0-beta.4, < 5.0.0-beta.32

## Severity

- GitHub_M 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`
- GitHub 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`

## Exploitation

- 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.

## Sources

- [GitHub Advisory GHSA-8fpg-xm3f-6cx3](https://github.com/advisories/GHSA-8fpg-xm3f-6cx3)
- [CVE.org record CVE-2026-73421](https://www.cve.org/CVERecord?id=CVE-2026-73421)
- [NVD entry CVE-2026-73421](https://nvd.nist.gov/vuln/detail/CVE-2026-73421)
- [github.com](https://github.com/nextauthjs/next-auth/security/advisories/GHSA-8fpg-xm3f-6cx3)
- [github.com](https://github.com/nextauthjs/next-auth/commit/d008b9b764bf4b322a87e1822d1dda7789258d8f)
- [github.com](https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32)

---
Source page: https://erroneo.us/security/cve/CVE-2026-73421/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt