CVE-2026-104970: Makeplane Plane

High severity, CVSS 8.1. EPSS: 0.3% chance of exploitation in the next 30 days.

Plane is an open-source project management tool. From 0.13 until 1.4.0, InstanceAdminSignUpEndpoint in apps/api/plane/license/api/views/admin.py:89-117, 173-229 uses InstanceAdmin.objects.first() for the first-admin check and performs account creation without an atomic transaction, row lock, uniqueness guard, or advisory lock. Two concurrent unauthenticated requests with different email addresses can both observe that no instance administrator exists, create separate User and InstanceAdmin rows, and receive sessions with instance-admin authority. This allows an attacker to share unrestricted instance administration with the legitimate operator. This issue is fixed in 1.4.0.

Affected products

• Makeplane Plane: before 1.4.0 (fixed in 1.4.0)

Published 2026-10-05. Last modified 2026-10-06.