Incorrect Behavior Order: Validate Before Canonicalize Affecting @auth/core package, versions >=0.1.0 <0.41.3
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-AUTHCORE-18306877
- published25 Jul 2026
- disclosed23 Jul 2026
- creditkakashi-kx
Introduced: 23 Jul 2026
NewCVE-2026-73420 (opens in a new tab)How to fix?
Upgrade @auth/core to version 0.41.3 or higher.
Overview
@auth/core is an Authentication for the Web.
Affected versions of this package are vulnerable to Incorrect Behavior Order: Validate Before Canonicalize in the email/magic-link sign-in process. An attacker can gain unauthorized access to a victim's account by submitting an email address containing Unicode homoglyphs that bypass validation, causing the passwordless sign-in link to be delivered to an attacker-controlled mailbox. This is only exploitable if the email/magic-link provider is enabled, the default identifier normalizer is used, and the mail delivery service applies Unicode normalization to recipient addresses.
Workaround
This vulnerability can be mitigated by supplying a custom normalizeIdentifier that normalizes the identifier using NFKC before validation, or by rejecting addresses with non-ASCII characters if internationalized email addresses are not required.