CVE-2026-73420
CriticalCVSS 9.1Exploitation Probability (EPSS)
Low risk44th percentile - higher than 44% of all known CVEs
Summary
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.
Other vulnerabilities in NextAuth.js
See all- CVE-2026-73421Critical
NextAuth.js from 5.0.0-beta.0 until 5.0.0-beta.32 has a vulnerability where applications that gate access by checking only for the existence of the auth object can fail open when Auth.js has a server configuration error. A non-OK session response is parsed into a truthy error object instead of null, so checks such as !!auth evaluate to true for unauthenticated requests.
- CVE-2026-73419Medium
NextAuth.js before @auth/core 0.41.3, next-auth 4.24.15, and 5.0.0-beta.32 stores OAuth/OIDC anti-CSRF state, nonce, and PKCE verifier in global cookies not bound to the provider. An attacker can exploit this to link their account to a victim's account in multi-provider apps with account linking.
- CVE-2026-73418High
NextAuth.js before @auth/core 0.41.3, next-auth 4.24.15, and 5.0.0-beta.32 can throw an uncaught exception in getToken() when reading a malformed Authorization: Bearer header. When no session cookie is present, getToken() URL-decodes the bearer value before validation, and malformed percent encoding causes decodeURIComponent() to throw. This can lead to per-request denial of service without exposing tokens or bypassing authentication.
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS