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high advisory

CVE-2026-9227: GutenBee WordPress Plugin Arbitrary File Upload

The GutenBee – Gutenberg Blocks plugin for WordPress is vulnerable to arbitrary file upload, allowing authenticated attackers with author-level access to achieve remote code execution by uploading executable files with double extensions.

CVE-2026-9227 describes an arbitrary file upload vulnerability affecting the GutenBee – Gutenberg Blocks plugin for WordPress in versions up to and including 2.20.1. The vulnerability resides in the gutenbee_file_and_ext_json function, which implements a flawed file extension validation check. Specifically, the code uses strpos() to check if the filename contains ‘.json’, but fails to verify that the filename actually ends with ‘.json’. This allows attackers to bypass the intended validation by using double extensions such as ‘shell.json.php’. An attacker must be authenticated with author-level privileges or higher to exploit this vulnerability. Successful exploitation allows the attacker to upload arbitrary files, including executable scripts, leading to remote code execution on the vulnerable WordPress server.

Attack Chain

  1. An attacker authenticates to the WordPress site with author-level or higher privileges.
  2. The attacker navigates to a page or post editing interface where the GutenBee plugin’s file upload functionality is available.
  3. The attacker crafts a malicious file with a double extension, such as shell.json.php.
  4. The attacker uses the GutenBee plugin’s file upload functionality to upload the crafted file. The flawed strpos() check in gutenbee_file_and_ext_json incorrectly validates the file extension.
  5. The file is uploaded to the WordPress uploads directory.
  6. The attacker accesses the uploaded file via a direct HTTP request to the file’s location.
  7. The web server executes the PHP code within the uploaded file.
  8. The attacker achieves remote code execution on the WordPress server.

Impact

Successful exploitation of CVE-2026-9227 allows an authenticated attacker with author-level access or higher to execute arbitrary code on the target WordPress server. This can lead to complete compromise of the server, including data theft, website defacement, or further malicious activities. The vulnerability affects all WordPress sites using the GutenBee plugin with versions 2.20.1 or lower, potentially impacting a wide range of websites.

Recommendation

  • Upgrade the GutenBee – Gutenberg Blocks plugin to the latest version to patch CVE-2026-9227.
  • Deploy the Sigma rule “Detect CVE-2026-9227 GutenBee Arbitrary File Upload Attempt” to your SIEM to detect potential exploitation attempts in web server logs.
  • Implement stricter file extension validation on the server-side to prevent similar arbitrary file upload vulnerabilities.

Detection coverage 2

Detect CVE-2026-9227 GutenBee Arbitrary File Upload Attempt

high

Detects CVE-2026-9227 exploitation — Attempts to upload files with double extensions (e.g., .json.php) to the GutenBee plugin upload handler.

sigma tactics: execution, initial_access sources: webserver

Detect WordPress AJAX File Upload with Suspicious Extensions

medium

Detects attempts to upload files with suspicious extensions via WordPress AJAX, which may indicate exploitation of vulnerabilities like CVE-2026-9227.

sigma tactics: execution, initial_access sources: webserver

Detection queries are available on the platform. Get full rules →