---
title: "CVE-2026-73420: Auth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass"
url: https://erroneo.us/security/cve/CVE-2026-73420/
description: "CVE-2026-73420 (@auth/core (npm)): NextAuth.js provides authentication for Next.js. Prior to @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32, the…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-08-13
date_modified: 2026-08-14
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-73420"
kev: false
cvss: 9.1
epss: 0.00725
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-73420: Auth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass

**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 0.7% , percentile 53: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 53% 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 @auth/core (npm) >= 0.1.0, < 0.41.3, fixed in 0.41.3 ; next-auth (npm) >= 4.10.3, < 4.24.15, fixed in 4.24.15 ; next-auth (npm) >= 5.0.0-beta.1, <= 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. Prior to @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32, the defaultNormalizer used by the email and magic-link sign-in flow validates an address before applying Unicode normalization. An address can contain a Unicode character such as U+FF20 FULLWIDTH COMMERCIAL AT that is not ASCII at-sign but canonicalizes to an ASCII at-sign under NFKC or NFKD normalization. The address passes the normalizer's single-at-sign check, but a downstream sendVerificationRequest mail library or delivery service that normalizes the address can then see two at-sign separators and deliver the passwordless sign-in link to an attacker-controlled recipient. Applications are affected when the email provider uses the built-in normalizer rather than a custom normalizeIdentifier and the downstream sender applies Unicode normalization. An attacker who knows a victim's email address can request the misrouted magic link and sign in as the victim without victim interaction. This issue is fixed in @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32.

## Affected packages

- npm `@auth/core` >= 0.1.0, < 0.41.3 → fixed: 0.41.3
- npm `next-auth` >= 4.10.3, < 4.24.15 → fixed: 4.24.15
- npm `next-auth` >= 5.0.0-beta.1, <= 5.0.0-beta.31 → fixed: 5.0.0-beta.32

## Affected products (CVE record)

- nextauthjs next-auth: < 4.24.15, >= 5.0.0-beta.4, < 5.0.0-beta.32
- @auth core: >= 0.1.0, < 0.41.3

## 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 total .
- FIRST EPSS (model of 2026-10-21): 0.73% probability of exploitation activity in the next 30 days; percentile 53.

## Sources

- [GitHub Advisory GHSA-7rqj-j65f-68wh](https://github.com/advisories/GHSA-7rqj-j65f-68wh)
- [CVE.org record CVE-2026-73420](https://www.cve.org/CVERecord?id=CVE-2026-73420)
- [NVD entry CVE-2026-73420](https://nvd.nist.gov/vuln/detail/CVE-2026-73420)
- [github.com](https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh)
- [github.com](https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94)
- [github.com](https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0)
- [github.com](https://github.com/nextauthjs/next-auth/releases/tag/@auth/core@0.41.3)
- [github.com](https://github.com/nextauthjs/next-auth/releases/tag/next-auth@4.24.15)
- [github.com](https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32)

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Source page: https://erroneo.us/security/cve/CVE-2026-73420/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt