Executive Summary

CVE-2026-56701 is an XML External Entity (XXE) injection vulnerability in Grav CMS versions before 2.0.0-beta.2. It occurs during the processing of uploaded SVG files, where the application uses the function simplexml_load_string without disabling external entity loading.

This flaw allows authenticated attackers to upload malicious SVG files containing XXE payloads. When processed, these payloads enable the attacker to read arbitrary files on the server by exploiting the XML parser's external entity feature.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability can have significant impacts, primarily on the confidentiality of your data.

• Authenticated attackers can read arbitrary files on the server, including sensitive files such as /etc/passwd, user configuration files, environment secrets, and API keys.
• It also poses risks of Server-Side Request Forgery (SSRF), where attackers can make the server perform unintended requests.
• There is a potential for Denial of Service (DoS) attacks through recursive entity expansion.

The vulnerability has a moderate to high severity with CVSS scores of 7.1 (v4) and 6.5 (v3.1), indicating a serious risk to confidentiality but no direct impact on integrity or availability.

Useful 0 Not Useful 0

Detection Guidance

This vulnerability can be detected by identifying if your Grav CMS instance is running a version before 2.0.0-beta.2 and if it processes SVG file uploads using the vulnerable XML parser configuration.

To detect exploitation attempts, monitor for uploads of SVG files containing suspicious XML external entity (XXE) payloads.

While no specific commands are provided in the resources, typical detection methods include:

• Inspect uploaded SVG files for presence of <!DOCTYPE> or <!ENTITY> declarations which are indicators of XXE payloads.
• Use network monitoring tools to detect unusual outbound requests or data exfiltration patterns originating from the Grav server.
• Check server logs for authenticated user uploads of SVG files and any related errors or suspicious activity.

Useful 0 Not Useful 0

Mitigation Strategies

The immediate mitigation step is to upgrade Grav CMS to version 2.0.0-beta.2 or later, where the vulnerability has been patched.

The patch removes <!DOCTYPE> and <!ENTITY> declarations from SVG files before parsing and applies security flags to disable external entity loading, effectively preventing XXE attacks.

Additionally, ensure that only trusted authenticated users can upload SVG files and consider disabling SVG uploads if not necessary.

Implement monitoring for suspicious SVG uploads and unusual outbound network activity as a secondary defense.

Useful 0 Not Useful 0

Compliance Impact

This vulnerability allows authenticated attackers to read arbitrary files on the server, including sensitive data such as user configuration files, environment secrets, and API keys.

The exfiltration of sensitive data due to this XML External Entity (XXE) injection vulnerability can lead to unauthorized disclosure of personal or confidential information.

Such unauthorized data exposure can negatively impact compliance with data protection standards and regulations like GDPR and HIPAA, which require safeguarding sensitive and personal data against unauthorized access.

Useful 0 Not Useful 0