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TI-2026-74553 Aliases CVE-2026-110863

Authentication bypass in Better Auth SSO lets users sign in as others

Priority LOW 39CWE-287Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Security bypass
Confidentiality · integrity · availability
High · High · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-287.

Summary

The @better-auth/sso package from 1.7.0-rc.2 before 1.7.3 contains an authentication bypass caused by improper authentication (CWE-287). Account lookup ignores providerId, so an authenticated user can register a personal SSO provider that copies a legitimate provider's OIDC issuer or SAML entity ID and assert a victim's subject or NameID. This creates sessions for the victim's account.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00269 19th percentileScored 2026-11-07
Fix Fixed sso (better-auth): 1.7.3

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
better-authsso1.7.0-rc.2 to before 1.7.31.7.3Patch availableCNA
  • sso Vendorbetter-auth Affected 1.7.0-rc.2 to before 1.7.3 Fixed in 1.7.3 Patch available CNA

Remediation

Update @better-auth/sso to version 1.7.3, which fixes the flaw.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

  • Fix · CNA sso (better-auth) Fixed in 1.7.3

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-15 Threatist record created from CVE-2026-110863
  2. 2026-10-16 Priority changed: MEDIUM → LOW
  3. 2026-10-16 CISA SSVC decision points changed
  4. 2026-11-06 Affected versions changed · Red Hat
  5. 2026-11-06 CVSS score added · Red Hat

References

Advisory 1

  • TI-2025-38277 Better Auth: Unauthenticated API key creation through api-key plugin CVSS 4.0CRITICAL 9.3
  • TI-2026-47627 better-auth SCIM 1.5.0 before 1.7.0-beta.4 Authorization Bypass CVSS 4.0HIGH 8.7
  • TI-2025-20000 Beter Auth has an Open Redirect via Scheme-Less Callback Parameter CVSS 4.0MEDIUM 6.9
  • TI-2026-13066 better-auth better-icons scan_project_icons/sync_icon path traversal CVSS 4.0MEDIUM 4.8
  • TI-2026-79320 OAuth state accepted as Magic Link token in Better Auth CVSS 3.1CRITICAL 9.1
  • TI-2026-74552 Authentication bypass in Better Auth Magic Link verification CVSS 4.0CRITICAL 9.3
See all 39 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences