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CVE-2026-73420

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

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 9.1 · Critical · EPSS 0.7% · Fix available

Published
Updated

Stack: node

Affected products and versions

  • next-auth

    Versions
    • < 4.24.15: Affected
    • >= 5.0.0-beta.4, < 5.0.0-beta.32: Affected

    No fix published

  • core

    Versions
    • >= 0.1.0, < 0.41.3: Affected

    No fix published

  • @auth/core npm

    Affected ranges
    • SEMVER: ≥ 0.1.0, < 0.41.3

    Update to 0.41.3

  • next-auth npm

    Affected ranges
    • SEMVER: ≥ 4.10.3, < 4.24.15

    Update to 4.24.15

  • next-auth npm

    Affected ranges
    • SEMVER: ≥ 5.0.0-beta.1, < 5.0.0-beta.32

    Update to 5.0.0-beta.32

Original sources

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