CVE-2026-73420
CriticalCVSS 9.1Summary
NextAuth.js prior to @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32 has a vulnerability in the email normalizer, where an address with a fullwidth at-sign (U+FF20) passes validation but after Unicode normalization becomes a standard @, potentially causing the sign-in link to be delivered to an attacker.
Risk Assessment
An attacker who knows a victim's email address can intercept the magic link and sign in as the victim, leading to account takeover.
Recommendation
Upgrade @auth/core to version 0.41.3 and next-auth to version 4.24.15 or 5.0.0-beta.32, which contain the fix.
Original NVD description (English source)
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.