Vulnerability · Published Aug 13, 2026 · Assigned by GitHub_M
CVE-2026-73420NextAuth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass
Critical 9.1
In plain English
A critical-severity security flaw in core from @auth. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 54% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | @auth/core | 0.41.3 | GHSA-7rqj-j65f-68wh |
| npm | next-auth | 4.24.15 | GHSA-7rqj-j65f-68wh |
| npm | next-auth | 5.0.0-beta.32 | GHSA-7rqj-j65f-68wh |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| nextauthjs | next-auth | < 4.24.15>= 5.0.0-beta.4, < 5.0.0-beta.32 |
| @auth | core | >= 0.1.0, < 0.41.3 |
Weakness: CWE-180 · 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
References
- https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh x_refsource_CONFIRM
- https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94 x_refsource_MISC
- https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0 x_refsource_MISC
- https://github.com/nextauthjs/next-auth/releases/tag/@auth/core@0.41.3 x_refsource_MISC
- https://github.com/nextauthjs/next-auth/releases/tag/next-auth@4.24.15 x_refsource_MISC
- https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32 x_refsource_MISC