Vulnerability in @auth/core (CVE-2026-73420)
Summary
Vulnerability in @auth/core (CVE-2026-73420). Risk of unauthorized operations or information disclosure. Exploitable via normalizeIdentifier. Mitigation: upgrade to 0.41.3 or later.
Original description
The description as published by the source.
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, < 4.24.14, or@auth/core>= 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
sendVerificationRequestimplementation uses a mail library or delivery service that applies Unicode normalization to recipient addresses (most internationalized-email/SMTPUTF8-capable senders do).
You are not affected if you do not use the email provider, or if your normalizer/mailer rejects or canonicalizes non-ASCII addresses before they are validated.
Impact
- Account takeover: an attacker who knows a victim's email address can request a magic link that is deliver…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-73420 has been found in @auth/core.
Attackers can target a specific entry point like normalizeIdentifier over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade @auth/core to 0.41.3 or later.
If unsure, ask your IT team or search "@auth/core CVE-2026-73420" on the vendor's site.
CVE-2026-73420 (@auth/core) — CWE-180
Attack surface: normalizeIdentifier / sendVerificationRequest
Patched: 0.41.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-180) exists in @auth/core. Attackers reach the vulnerable code path via normalizeIdentifier.
Check the vendor advisory for the affected versions of @auth/core. Attack surface: normalizeIdentifier / sendVerificationRequest.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 0.41.3.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r '@auth/core' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r '@auth/core' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
@auth/coreを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade @auth/core to 0.41.3ステージング環境で 0.41.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。