Critical
CVSS 9.8 Auth Bypass Private Engagement
Disclosure
NextAuth Authentication Bypass via Social Login Flow
NextAuth callback accepts attacker-controlled userId without proving social identity ownership, issuing session for arbitrary users.
- Target
- European iGaming Platform
- Category
- Auth Bypass
- Channel
- Private Engagement
- Disclosed
- 2026-04
Redaction note
Vendor identity withheld.
This finding is documented here as part of MemCyber’s public disclosure record. The vendor has been anonymized to a sector and region descriptor. Full technical detail — including root cause, reproducible proof-of-concept, remediation guidance, and vendor attribution where granted — is available to qualified prospects under NDA.
Coordinated disclosure
How we handled it.
- Reported to the vendor via Private Engagement with a reproducible proof-of-concept.
- Triage + remediation window coordinated with the vendor security team.
- Fix verified before any public reference.
- This record published only after the embargo period closed.