supabase auth up to 2.184.x Token Endpoint authentication spoofing

Summaryinfo

A vulnerability, which was classified as critical, has been found in supabase auth up to 2.184.x. The affected element is an unknown function of the component Token Endpoint. The manipulation leads to authentication spoofing. This vulnerability is uniquely identified as CVE-2026-31813. The attack is possible to be carried out remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in supabase auth up to 2.184.x. It has been rated as critical. This issue affects an unknown functionality of the component Token Endpoint. The manipulation with an unknown input leads to a authentication spoofing vulnerability. Using CWE to declare the problem leads to CWE-290. This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Supabase Auth is a JWT based API for managing users and issuing JWT tokens. Prior to 2.185.0, a vulnerability has been identified that allows an attacker to issue sessions for arbitrary users using specially crafted ID tokens when the Apple or Azure providers are enabled. The attacker issues a valid, asymmetrically signed ID token from their issuer for each victim email address, which then is sent to the Supabase Auth token endpoint using the ID token flow. If the ID token is OIDC compliant, the Auth server would validate it against the attacker-controlled issuer and link the existing OIDC identity (Apple or Azure) of the victim to an additional OIDC identity based on the ID token contents. The Auth server would then issue a valid user session (access and refresh tokens) at the AAL1 level to the attacker. This vulnerability is fixed in 2.185.0.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-31813 since 03/09/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available.

Upgrading to version 2.185.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-11239). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

• supabase

Name

• auth

Version

• 2.184

Website

• Product: https://github.com/supabase/auth/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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