Vulnerability · Published Oct 14, 2026 · Assigned by VulnCheck

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

High 8.1

In plain English

A high-severity improper authentication in sso from better-auth. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities).

Severity (CVSS 3.1)8.1High

Exploit odds (30 days)0.3%top 80.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
better-auth	sso	1.7.0-rc.2 – before 1.7.3

Weakness: CWE-287 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

References

GitHub Security Advisory (GHSA-mx9r-x6ww-qjw9) vendor-advisory
VulnCheck Advisory: Better Auth @better-auth/sso before 1.7.3 Authentication Bypass via Personal SSO Providers third-party-advisory