# 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.

- **Severity:** Critical 10.0 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Jul 2026
- **Updated:** 28 Jul 2026
- **Also known as:** GHSA-8449-9vw6-7mp5

## 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 (Improper Control of Generation of Code)

## 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.

## 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:

- https://github.com/0xdak/CVE-2025-71389_exploit (github_poc): https://github.com/0xdak/CVE-2025-71389_exploit

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-71389 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2025-71389 in the wild and no public exploit code.

Affected product: calcom cal.diy. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-71389/ (Markdown: https://insights.sbomify.com/CVE-2025-71389/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-71389
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-71389
- OSV: https://osv.dev/vulnerability/CVE-2025-71389

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-71389/
Summaries are generated and may contain mistakes; the official description above is the record.