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

Quick assessment

Affected
nextauthjs next-auth
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Auth.js是Auth.js组织的一款身份验证开发框架。 Auth.js 0.41.3之前版本、next-auth 4.24.15之前版本和5.0.0-beta.32之前版本存在处理逻辑错误漏洞，该漏洞源于默认规范化器在Unicode规范化之前验证地址，包含全角@的地址通过单个@检查后，被下游邮件服务标准化为两个@分隔符，导致无密码登录链接被发送给攻击者控制的收件人，攻击者可在无受害者交互的情况下请求该链接并以受害者身份登录。

CVSS 9.1 · Critical EPSS 0.73% · P53

Possible ATT&CK Techniques 1 AI

T1110.001 · Password Guessing

Affected Version Matrix 3

VendorProduct Version RangeStatus
@auth core >= 0.1.0, < 0.41.3 affected
nextauthjs next-auth < 4.24.15 affected
>= 5.0.0-beta.4, < 5.0.0-beta.32 affected
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I. Basic Information for CVE-2026-73420

Vulnerability Information
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Vulnerability Title
NextAuth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
不正确的行为次序：规范化之前验证
Source: CVE Program / CVE List V5
Vulnerability Title
Auth.js 处理逻辑错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Auth.js是Auth.js组织的一款身份验证开发框架。 Auth.js 0.41.3之前版本、next-auth 4.24.15之前版本和5.0.0-beta.32之前版本存在处理逻辑错误漏洞，该漏洞源于默认规范化器在Unicode规范化之前验证地址，包含全角@的地址通过单个@检查后，被下游邮件服务标准化为两个@分隔符，导致无密码登录链接被发送给攻击者控制的收件人，攻击者可在无受害者交互的情况下请求该链接并以受害者身份登录。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
nextauthjs next-auth < 4.24.15 -
@auth core >= 0.1.0, < 0.41.3 -

II. Public POCs for CVE-2026-73420

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 7715 chars
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III. Intelligence Information for CVE-2026-73420

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Patches & Fixes for CVE-2026-73420 (3)

Vendor Advisories for CVE-2026-73420 (1)

Vendor Pages for CVE-2026-73420 (2)

IV. Related Vulnerabilities

Same product: next-auth
Same vendor: nextauthjs
Same weakness: CWE-180

V. Comments for CVE-2026-73420

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