Is CVE-2025-71389 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2025-71389 being exploited in the wild.

How severe is CVE-2025-71389?

Critical severity, with a CVSS score of 10, published 23 July 2026.

Is there a fix for CVE-2025-71389?

A patch was published on 2025-12-04: Cal.com merged PR to bump Next.js version Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2025-71389 attacked?

It is attacked over the network, in a web application.

Am I affected by CVE-2025-71389?

Check whether you run Cal.Com at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2025-71389: Cal.com remote code execution via Next.js RSC deserialization

CVE-2025-71389 · Severity: critical · CVSS 10 · Published 2026-07-23

Cal.com is an open-source scheduling platform used by businesses to manage appointments and meetings. A critical security flaw allows an unauthenticated attacker to remotely execute malicious code on the server hosting the application. This could lead to a complete system takeover, theft of sensitive customer data, or disruption of scheduling services.

Technologies: Cal.Com. Vendors: Cal.com.

Quick answers

Is CVE-2025-71389 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2025-71389 being exploited in the wild.
How severe is CVE-2025-71389?: Critical severity, with a CVSS score of 10, published 23 July 2026.
Which products and versions are affected?: Cal.Com < 5.9.9.
Is there a fix for CVE-2025-71389?: A patch was published on 2025-12-04: Cal.com merged PR to bump Next.js version Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2025-71389 attacked?: It is attacked over the network, in a web application.
Am I affected by CVE-2025-71389?: Check whether you run Cal.Com at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

Cal.com (cal.diy) versions prior to 5.9.9 are vulnerable to remote code execution (RCE) due to an upstream vulnerability in Next.js (CVE-2025-55182). The flaw exists in the React Server Components (RSC) request handling, where the server deserializes attacker-controlled input from the React flight protocol. A remote, unauthenticated attacker can send a specially crafted RSC request to trigger the execution of arbitrary code during server-side processing. The vulnerability is rooted in the 'react-server-dom-webpack' (and related) packages used by Next.js App Router. The issue is resolved in Cal.com 5.9.9 by updating the Next.js dependency to a patched version (e.g., 15.5.7 or 15.4.8).

Affected products

Cal.com cal.diy < 5.9.9

Timeline

2025-12-03: advisory: Upstream Next.js vulnerability disclosed (GHSA-9qr9-h5gf-34mp)
2025-12-04: patched: Cal.com merged PR to bump Next.js version
2025-12-07: advisory: Cal.com published security advisory GHSA-qjx2-5xqp-cpf4
2026-07-23: disclosed: CVE-2025-71389 published to NVD

References

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