What’s Vulnerable › Vulnerabilities

CVE-2026-110863: Better Auth @better-auth/sso before 1.7.3 Authentication Bypass via Personal SSO Providers

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-14 · updated 2026-10-16
• Weakness: CWE-287

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.

Affected products

• better-auth sso: from 1.7.0-rc.2 before 1.7.3 — fixed in 1.7.3

How to fix

Upgrade to a fixed version: better-auth sso 1.7.3. Check the vendor advisory for mitigations.

References

• https://github.com/better-auth/better-auth/security/advisories/GHSA-mx9r-x6ww-qjw9
• https://www.vulncheck.com/advisories/better-auth-better-auth-sso-before-1.7.3-authentication-bypass-via-personal-sso-providers

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