GHSA-7rqj-j65f-68wh
ADVISORY - githubSummary
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 delivered to an attacker-controlled mailbox, then use it to sign in as the victim.
- No victim interaction is required to misroute the link; the attacker initiates the flow.
Patched version
The fix applies Unicode (NFKC) normalization before the address is validated, so homoglyph separators are collapsed and rejected up front. Upgrade to the first release containing this fix (pending; this advisory will be updated with the exact patched version before publication). No application code changes are required after upgrading.
Workarounds
If you cannot upgrade immediately:
- Supply a custom
normalizeIdentifieron the email provider that callsidentifier.normalize("NFKC")(and lower-cases/trims) before any validation, and rejects addresses that do not contain exactly one@after normalization. - Or reject any address whose local part or domain contains non-ASCII characters, if your user base does not require internationalized email addresses.
Credit
Reported by @kakashi-kx. Thank you for the responsible disclosure.
Common Weakness Enumeration (CWE)
Incorrect Behavior Order: Validate Before Canonicalize
GitHub
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CVSS SCORE
9.1critical| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| next-auth | npm | - | - | >=4.10.3,<4.24.15 | 4.24.15 |
| @auth/core | npm | - | - | >=0.1.0,<0.41.3 | 0.41.3 |
| next-auth | npm | - | - | >=5.0.0-beta.1,<=5.0.0-beta.31 | 5.0.0-beta.32 |
CVSS:4 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.
The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: A race condition must be won to successfully exploit the vulnerability. The successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker. The attack may need to be launched multiple times against a single target before being successful. Network injection. The attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges.
There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Vulnerable System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Vulnerable System.
There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
There is no impact to availability within the Vulnerable System.
There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.