CVE-2026-28793 is a path traversal vulnerability classified under CWE-22 affecting the @tinacms CLI development server versions prior to 2.1.8. TinaCMS is a headless content management system, and its CLI tool includes a development server that exposes media-related HTTP endpoints on the local machine, typically on port 4001. These endpoints (/media/list/*, /media/upload/*, /media/*) accept user-controlled path segments which are processed using JavaScript functions decodeURI() and path.join(). However, the implementation lacks proper validation to ensure that the resolved filesystem path remains confined within the designated media directory. This improper limitation allows an attacker with access to the development server to craft specially encoded path traversal sequences (e.g., ../) to escape the media directory and access arbitrary files on the host filesystem. The attacker can read sensitive files or write malicious files, potentially leading to full compromise of the development environment. The vulnerability does not require authentication or user interaction, but exploitation is limited to environments where the development server is accessible. The CVSS v3.1 base score is 8.4 (high), reflecting the ease of exploitation and the high impact on confidentiality, integrity, and availability. The issue was resolved in TinaCMS CLI version 2.1.8 by adding proper path validation to restrict file operations within the intended directory. No known exploits are reported in the wild as of the publication date.

The vulnerability allows attackers to read and write arbitrary files on the filesystem hosting the TinaCMS CLI development server. This can lead to disclosure of sensitive information such as source code, configuration files, credentials, or other private data stored on the system. Writing arbitrary files can enable attackers to plant malicious scripts or binaries, potentially leading to further compromise of the development environment or pivoting to other systems. Since the development server often runs with the privileges of the developer, the impact can be significant, including loss of integrity and availability of critical files. Although the server is typically local and not exposed to the internet by default, misconfigurations or use in shared or cloud environments could increase exposure. Organizations relying on TinaCMS CLI for development risk intellectual property theft, disruption of development workflows, and potential escalation of privileges if exploited.

Upgrade the TinaCMS CLI to version 2.1.8 or later, where the path traversal vulnerability is fixed by enforcing strict validation of file paths to ensure they remain within the media directory. Until upgrading, restrict access to the development server (default port 4001) using firewall rules or network segmentation to trusted users only. Avoid exposing the development server to untrusted networks or the internet. Developers should avoid running the CLI with elevated privileges and consider running it inside isolated environments such as containers or virtual machines to limit potential damage. Implement monitoring and logging of access to the development server endpoints to detect suspicious activity. Review and audit file system permissions to minimize the impact of any unauthorized file access or modification. Educate development teams about the risks of running development servers with exposed endpoints and encourage prompt patching of dependencies.