CVE-2026-110863

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Authentication Bypass in Better Auth SSO

Publication date: 2026-10-14

Last updated on: 2026-10-16

Assigner: VulnCheck

Description

Better Auth @better-auth/sso from 1.7.0-rc.2 before 1.7.3 contains an authentication bypass vulnerability that allows authenticated users to sign in as other users by registering a personal SSO provider. Attackers can copy a legitimate provider's OIDC issuer or SAML entity ID and assert a victim's subject or NameID, because account lookup ignores providerId, creating sessions for victim accounts.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-10-14

Last Modified

2026-10-16

Generated

2026-10-19

AI Q&A

2026-10-15

EPSS Evaluated

2026-10-18

NVD

CVE-2026-110863

EUVD

EUVD-2026-101746

Affected Vendors & Products

Vendor	Product	Version / Range
better-auth	sso	1.7.0-rc.2

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-287	When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

Attack-Flow Graph

Executive Summary

Better Auth's SSO component (versions 1.7.0-rc.2 to 1.7.2) has an authentication bypass flaw. Authenticated users can register a malicious SSO provider that mimics a legitimate one. By copying the OIDC issuer or SAML entity ID of a victim's provider, attackers can impersonate the victim during login. The system fails to properly validate provider IDs during account lookup, allowing session hijacking for any user account.

Impact Analysis

If you use Better Auth SSO in your application, attackers with valid credentials could gain access to other users' accounts. This could lead to unauthorized data access, privilege escalation, or complete account takeover. The impact depends on the data stored in those accounts and the application's functionality.

Compliance Impact

This vulnerability likely violates compliance requirements for data protection and access controls. GDPR requires proper authentication and authorization mechanisms to protect personal data. HIPAA mandates secure access to protected health information. The flaw could lead to unauthorized data exposure, triggering breach notification requirements and potential fines.

Mitigation Strategies

Immediately update Better Auth SSO to version 1.7.3 or later to patch the authentication bypass vulnerability. Review and restrict user permissions to minimize potential misuse of SSO provider registration. Monitor logs for unusual authentication attempts or sessions tied to unexpected provider IDs.

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