CVE-2025-71389 Cal.com before 5.9.9 Remote Code Execution via RSC
Unauthenticated attackers can execute arbitrary code on Cal.com servers by sending crafted React Server Components requests due to unsafe deserialization.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-71389?
CVE-2025-71389 is a critical unsafe deserialization vulnerability in calcom cal.diy, published on 23 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-94
Which versions are affected by CVE-2025-71389?
How do I fix CVE-2025-71389?
No fix has been published for CVE-2025-71389 yet. Limit exposure of the affected software until one is available.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2025-71389 being exploited?
There is no known exploitation of CVE-2025-71389 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as GHSA-8449-9vw6-7mp5.