Exploit for CVE-2026-23478

## https://sploitus.com/exploit?id=08297B8D-5FD1-59EC-957D-CEE89E59EC70
# 🔐 CVE-2026-23478 — Critical Authentication Bypass

![Critical cal com Vulnerability Let Attackers Bypass Authentication Via Fake TOTP Codes   (1)](https://github.com/user-attachments/assets/99d3e27d-b32b-478a-bc51-177b110ad5cf)

> **Severity:** 🔴 *Critical*
> **CVSS v4:** **10.0 / 10**
> **Published:** January 13, 2026

---

## 🧠 At a Glance

A **critical authentication bypass** vulnerability in **Cal.com** allows attackers to **fully impersonate any user**—no password required.

---

## 🎯 Affected Software

* **Product:** Cal.com (open-source scheduling platform)
* **Vulnerable Versions:** `3.1.6 → 6.0.6`
* **Patched Version:** ✅ `6.0.7+`

---

## 🧩 Root Cause

The issue stems from **improper server-side validation** in a custom **NextAuth JWT callback**.

### What went wrong?

* The backend **trusted client-supplied data**
* Specifically during `session.update()`
* Attackers could supply **any email address**
* The server accepted it as legitimate

🛑 This violates basic authentication and authorization boundaries.

---

## 💥 Impact

An unauthenticated attacker can:

* 👤 Log in as **any user**
* 📅 View & modify private schedules
* ❌ Cancel or create bookings
* 🔗 Abuse connected integrations
* 🧠 Pivot to deeper system access

**No credentials. No user interaction. Full account takeover.**

---

## 🧨 Attack Characteristics

| Factor              | Value                    |
| ------------------- | ------------------------ |
| Attack Vector       | Network                  |
| Privileges Required | None                     |
| User Interaction    | None                     |
| Exploit Complexity  | Low                      |
| Impact              | Total account compromise |

---

## 🧷 Vulnerability Classifications

* **CWE-602:** Client-Side Enforcement of Server-Side Security
* **CWE-639:** Authorization Bypass via User-Controlled Key

---

## 🛠️ Mitigation (Do This Now)

### ✅ Immediate Actions

1. **Upgrade Cal.com to `v6.0.7` or later**
2. **Rotate session tokens & auth secrets**
3. **Audit logs** for suspicious session updates
4. **Review custom NextAuth logic**

   * Never trust client-provided identity fields
   * Enforce strict server-side checks

---

## 🧯 Security Takeaway

> **Scheduling systems are identity systems.**
> Treat them with the same security rigor as authentication providers.

---