CVE-2026-110863: Improper Authentication in better-auth sso
Description
Better Auth sso versions from 1.7.0-rc.2 up to but not including 1.7.3 contain an authentication bypass vulnerability. This flaw allows authenticated users to impersonate other users by registering a personal SSO provider that mimics a legitimate provider's OIDC issuer or SAML entity ID. The vulnerability arises because account lookup ignores the providerId, enabling attackers to create sessions for victim accounts by asserting their subject or NameID.
CVSS v4.0
Score 8.6high
Affected software
better-auth
sso
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-110863 is an authentication bypass vulnerability in better-auth/sso affecting versions >=1.7.0-rc.2 and <1.7.3. Authenticated users can exploit this flaw by registering a personal SSO provider that copies a legitimate provider's OIDC issuer or SAML entity ID. Due to the account lookup process ignoring the providerId, attackers can assert a victim's subject or NameID and gain unauthorized access by creating sessions for those victim accounts.
Potential Impact
This vulnerability allows authenticated users to bypass authentication controls and impersonate other users, potentially gaining unauthorized access to victim accounts. The CVSS 4.0 score of 8.6 (high severity) reflects the network attack vector, low attack complexity, no privileges required, no user interaction, and high impact on confidentiality and integrity.
Mitigation Recommendations
No explicit patch or remediation information is provided in the input data. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict user permissions to limit who can register SSO providers and monitor for suspicious SSO provider registrations.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-10-14T22:18:33.239Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ad00a672cdf04f656ba0300
Added to database: 10/14/2026, 23:04:07 UTC
Last enriched: 10/14/2026, 23:18:27 UTC
Last updated: 10/14/2026, 23:20:01 UTC
Views: 3
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