CVE-2026-73420Network attack vectorHinoki check available

Account takeover via pre-normalization email validation

Published Aug 13, 2026 · Updated Aug 13, 2026

Email normalization in affected Auth.js packages allows remote attackers to take over accounts via misrouted passwordless sign-in links. The defaultNormalizer checks for a single ASCII at-sign before NFKC normalization, allowing a homoglyph to become a second separator during downstream mail handling. Affected releases require the email provider, built-in normalizer, and a sender that normalizes Unicode; no victim interaction is required.

CVSS severity9.1
Critical
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Email normalization in affected Auth.js packages allows remote attackers to take over accounts via misrouted passwordless sign-in links. The defaultNormalizer checks for a single ASCII at-sign before NFKC normalization, allowing a homoglyph to become a second separator during downstream mail handling. Affected releases require the email provider, built-in normalizer, and a sender that normalizes Unicode; no victim interaction is required.

The record

CVE
CVE-2026-73420
Published
Aug 13, 2026
Updated
Aug 13, 2026
Vendor
Auth.js
Product
@auth/core
Classifications
CWE-180, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 0.1.0, < 0.41.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Auth.js · @auth/coreversion=>= 0.1.0, < 0.41.3
Auth.js · NextAuth.jsversion=< 4.24.15; version=>= 5.0.0-beta.4, < 5.0.0-beta.32

Published CVSS scores

9.1GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-180Incorrect Behavior Order: Validate Before Canonicalize
T1078Valid Accounts

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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