# CVE-2026-73420

## Summary

- **CVE ID:** CVE-2026-73420
- **Severity:** CRITICAL
- **CVSS Score:** 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)
- **CWE:** CWE-180
- **Published:** Aug 13, 2026
- **Last Modified:** Aug 14, 2026

## 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.

## Affected Products

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

## References

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

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.53%
- **EPSS Percentile:** 43.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._