Auth bypass in Better-Auth Sso
CVE-2026-110863
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.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/better-auth/better-auth/security/advisories/GHSA-mx9r-x6ww-qjw9 (vendor-advisory)
- www.vulncheck.com/advisories/better-auth-better-auth-sso-before-1.7.3-authentic… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-110863?
- CVE-2026-110863 is a high-severity vulnerability in Better-Auth Sso, classified under Improper Authentication. CVSS score: 8.1/10. Published 2026-10-14.
- How severe is CVE-2026-110863?
- High severity. CVSS v3 base score is 8.1 out of 10.