vulnerability / NVI-00015275 / Revision 2
Auth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass
GitHub lists this reviewed advisory for @auth/core, next-auth, next-auth. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
9.1 CRITICAL (4.0)
security-advisories@github.com severity; no combined Null risk score.
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
@auth/core
source listed>= 0.1.0, < 0.41.3
## Summary The default email-address normalizer used by the email/magic-link sign-in flow validates the address **before** applying Unicode normalization. An address can contain a Unicode character that is not an ASCII `@` (U+0040) but canonicalizes to one under NFKC/NFKD normalization (the normalization commonly applied by mail libraries and services for internationalized email). Such an address passes the normalizer's single-`@` check, but a downstream mail library that normalizes the string then sees two `@` separators and may deliver the passwordless sign-in link to a different recipient than intended. This is an instance of validating before canonicalizing. ## Am I affected? You may be affected if **all** of the following hold: - You use `next-auth` `>= 4.0.0, = 0.1.0, < 0.41.3`. - You have the email / magic-link (passwordless) provider enabled. - You rely on the built-in default identifier normalizer (you have not supplied your own `normalizeIdentifier`). - Your `sendVerificationRequest` implementation uses a mail library or delivery service that applies Unicode normalization to recipient addresses (most internationalized-email/SMTPUTF8-capab
next-auth
source listed>= 4.10.3, < 4.24.15
## Summary The default email-address normalizer used by the email/magic-link sign-in flow validates the address **before** applying Unicode normalization. An address can contain a Unicode character that is not an ASCII `@` (U+0040) but canonicalizes to one under NFKC/NFKD normalization (the normalization commonly applied by mail libraries and services for internationalized email). Such an address passes the normalizer's single-`@` check, but a downstream mail library that normalizes the string then sees two `@` separators and may deliver the passwordless sign-in link to a different recipient than intended. This is an instance of validating before canonicalizing. ## Am I affected? You may be affected if **all** of the following hold: - You use `next-auth` `>= 4.0.0, = 0.1.0, < 0.41.3`. - You have the email / magic-link (passwordless) provider enabled. - You rely on the built-in default identifier normalizer (you have not supplied your own `normalizeIdentifier`). - Your `sendVerificationRequest` implementation uses a mail library or delivery service that applies Unicode normalization to recipient addresses (most internationalized-email/SMTPUTF8-capab
next-auth
source listed>= 5.0.0-beta.1, <= 5.0.0-beta.31
## Summary The default email-address normalizer used by the email/magic-link sign-in flow validates the address **before** applying Unicode normalization. An address can contain a Unicode character that is not an ASCII `@` (U+0040) but canonicalizes to one under NFKC/NFKD normalization (the normalization commonly applied by mail libraries and services for internationalized email). Such an address passes the normalizer's single-`@` check, but a downstream mail library that normalizes the string then sees two `@` separators and may deliver the passwordless sign-in link to a different recipient than intended. This is an instance of validating before canonicalizing. ## Am I affected? You may be affected if **all** of the following hold: - You use `next-auth` `>= 4.0.0, = 0.1.0, < 0.41.3`. - You have the email / magic-link (passwordless) provider enabled. - You rely on the built-in default identifier normalizer (you have not supplied your own `normalizeIdentifier`). - Your `sendVerificationRequest` implementation uses a mail library or delivery service that applies Unicode normalization to recipient addresses (most internationalized-email/SMTPUTF8-capab
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. NIST National Vulnerability Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
- NVD lastModified does not establish freshness of every associated CPE record.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-7rqj-j65f-68wh ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-73420 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Source facts changed; compare the preserved prior revision.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.