1. What is this vulnerability and why does it matter?

This vulnerability, identified as CVE-2024-27921, is a file upload path traversal flaw affecting Grav, an open-source, flat-file content management system. It allows attackers to replace or create files with various extensions such as .json, .zip, .css, or .gif. This is a critical security flaw because it poses severe risks, enabling attackers to inject arbitrary code on the server, undermine the integrity of backup files by overwriting existing ones or creating new ones, and exfiltrate sensitive data using CSS exfiltration techniques.

2. What are the CVSS score, severity level, and disclosure details?

The CVSS score for this vulnerability is 8.8. This indicates a High/Critical severity level.

• Published Date: 2024-03-21 21:38:29
• Modified Date: 2025-04-10 20:14:03

3. Which products, vendors, systems, and versions are affected?

• Product: Grav (an open-source, flat-file content management system)
• Affected Versions: All versions prior to 1.7.45.

4. What is the technical root cause and attack vector?

The technical root cause is a CWE-22 Path Traversal vulnerability within the file upload functionality of the Grav application. The attack vector involves an attacker leveraging the application's file upload mechanism to bypass directory restrictions and write files to arbitrary locations on the server.

5. How can this vulnerability be exploited?

This vulnerability can be exploited by an attacker uploading a specially crafted file that contains path traversal sequences (e.g., ../../) in its filename or metadata. This allows the attacker to replace or create files outside of the intended upload directory, including sensitive system files or web-accessible files. Successful exploitation can lead to:

• Arbitrary code injection on the server by uploading malicious scripts.
• Undermining the integrity of backup files by overwriting existing backups or creating new, malicious ones.
• Exfiltration of sensitive data using techniques such as CSS exfiltration by manipulating stylesheet files.

6. What mitigation steps and patches are available?

The primary mitigation step is to upgrade the Grav CMS application. Users should update to version 1.7.45 or newer, as this version contains the necessary patches to address the file upload path traversal vulnerability.

7. How can vulnerable systems be detected?

Vulnerable systems can be detected by checking the installed version of Grav CMS. Any Grav installation running a version older than 1.7.45 is considered vulnerable to CVE-2024-27921. Administrators should verify their Grav version number through the admin panel or by inspecting the application's files.

8. What are the indicators of compromise (IOCs)?

Specific indicators of compromise are not explicitly detailed in the provided CVE data. However, potential IOCs following an exploitation attempt might include:

• Presence of unexpected files with extensions like .json, .zip, .css, .gif in unusual or restricted directories.
• Modification timestamps on legitimate files that do not align with expected system activity.
• Unexpected changes or corruption of backup files.
• Suspicious outbound network connections from the Grav server, potentially indicating data exfiltration.

9. Which threat actors are known to exploit this vulnerability?

The provided CVE data does not specify any known threat actors currently exploiting CVE-2024-27921.

10. What public intelligence references and advisories exist?

• CVE ID: CVE-2024-27921
• CWE: CWE-22 (Path Traversal)
• Further details can typically be found in the official Grav project's security advisories or changelogs for version 1.7.45.

11. What is the risk assessment and urgency level?

The risk level for CVE-2024-27921 is assessed as High/Critical, as indicated by a CVSS score of 8.8. The vulnerability allows for arbitrary code injection, data exfiltration, and integrity compromise, leading to severe impacts on confidentiality, integrity, and availability. The urgency level for patching is Immediate. Organizations using affected Grav CMS versions should prioritize upgrading to version 1.7.45 without delay to prevent potential exploitation and mitigate severe business risks.