Compliance Impact

This vulnerability allows any authenticated user with rights to create or update a Git-backed stack in Portainer Community Edition to read arbitrary files accessible to the Portainer process. This unauthorized access to arbitrary files could potentially lead to exposure of sensitive or personal data.

Such unauthorized data exposure may impact compliance with data protection standards and regulations like GDPR and HIPAA, which require strict controls on access to sensitive information and protection against unauthorized disclosure.

However, the specific impact on compliance depends on the nature of the data exposed and the environment in which Portainer is deployed.

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Executive Summary

This vulnerability exists in Portainer Community Edition versions from 2.33.0 to before 2.33.8, 2.39.2, and 2.41.0. Portainer allows deploying stacks from Git repositories by cloning them using go-git v5. When cloning, Git blob entries with symlink mode are converted into real OS symlinks on the host filesystem without proper validation, except for the .gitmodules file.

Because of this, an attacker who can create or update a Git-backed stack (which is allowed by default for any authenticated user) can create a symlink in the repository pointing to an arbitrary file on the host system. When Portainer reads the stack entry point file, it follows the symlink and returns the contents of the target file in the HTTP response.

This means an attacker can read arbitrary files accessible to the Portainer process on the host system, potentially exposing sensitive information.

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Impact Analysis

This vulnerability allows any authenticated user with permissions to create or update Git-backed stacks to read arbitrary files on the host system where Portainer is running.

The impact includes unauthorized disclosure of sensitive information stored in files accessible to the Portainer process, which could include configuration files, credentials, or other confidential data.

Such unauthorized file access can lead to further attacks, compromise of the container environment, or leakage of sensitive business or personal data.

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Mitigation Strategies

To mitigate this vulnerability, upgrade Portainer Community Edition to one of the fixed versions: 2.33.8, 2.39.2, or 2.41.0.

Additionally, restrict or review user permissions to ensure that only trusted users have rights to create or update Git-backed stacks, as any authenticated user with such rights can exploit this vulnerability.

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Detection Guidance

This vulnerability can be detected by auditing existing Git-backed stack directories managed by Portainer for unexpected symbolic links, especially those pointing to sensitive files. Since the issue involves symlinks created from Git repositories, checking for symlinks in stack directories is a key detection method.

You can use commands to find symbolic links within the Portainer stack directories and inspect if any point to sensitive or unexpected locations.

• Use the find command to locate symlinks in the stack directory, for example: find /path/to/portainer/stacks -type l -ls
• Check the target of suspicious symlinks with: ls -l /path/to/symlink
• Review the contents of the docker-compose.yml files in the stacks to verify if they are symlinks: file /path/to/stack/docker-compose.yml

Additionally, monitoring HTTP requests to the GET /api/stacks/{id}/file endpoint for unusual file content responses or unexpected file reads may help detect exploitation attempts.

Restricting permissions to create or update Git-backed stacks and avoiding untrusted repositories are recommended preventive measures.

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