CVE-2025-71389: Calcom Cal.diy

Critical severity, CVSS 10.0. EPSS: 1.4% chance of exploitation in the next 30 days.

Cal.com (calcom/cal.diy) before 5.9.9 is vulnerable to unauthenticated remote code execution because it bundles a version of Next.js whose React Server Components (RSC) request handling deserializes attacker-controlled input. A remote attacker can send a crafted RSC request to the server and cause arbitrary code to be executed during server-side processing, without authentication or user interaction. The flaw derives from the upstream Next.js vulnerability CVE-2025-55182 and is resolved in 5.9.9 by updating the affected dependency.

Affected products

• Calcom Cal.diy: before 5.9.9 (fixed in 5.9.9)

Published 2026-07-23. Last modified 2026-09-29.