Executive Summary

This vulnerability exists in Grist spreadsheet software when using the 'pyodide' sandbox flavor to run Python formulas. Pyodide on Node.js does not provide an effective sandbox barrier, so if a user sets the environment variable GRIST_SANDBOX_FLAVOR to 'pyodide' and opens a malicious document, that document can execute arbitrary processes on the server hosting Grist. This allows an attacker to run unauthorized code on the server. The issue was fixed in Grist version 1.7.9 by running Pyodide under Deno, which provides a secure sandbox. As a workaround, users can switch to the gVisor-based sandbox by setting GRIST_SANDBOX_FLAVOR to 'gvisor'. [2]

Useful 0 Not Useful 0

Impact Analysis

This vulnerability can have severe impacts including unauthorized execution of arbitrary processes on the server hosting Grist. This can lead to unauthorized data access, data modification, and disruption of system availability. Since the vulnerability allows remote exploitation without any privileges or user interaction, it poses a critical risk to the confidentiality, integrity, and availability of the system and data. [2]

Useful 0 Not Useful 0

Detection Guidance

Detection can focus on checking the environment variable GRIST_SANDBOX_FLAVOR to see if it is set to 'pyodide', which indicates the vulnerable sandbox configuration. Additionally, monitoring for unexpected process executions originating from Grist server processes could indicate exploitation attempts. Since Grist is typically run in Docker containers, you can inspect the container environment variables with commands like `docker exec <container_id> printenv | grep GRIST_SANDBOX_FLAVOR`. Also, reviewing Grist version with `docker exec <container_id> grist --version` or checking the deployed version can help identify if it is prior to 1.7.9, which is vulnerable. [1, 2]

Useful 0 Not Useful 0

Mitigation Strategies

Immediate mitigation steps include upgrading Grist to version 1.7.9 or later, where the vulnerability is fixed by running Pyodide under Deno. If upgrading is not immediately possible, change the sandboxing method by setting the environment variable GRIST_SANDBOX_FLAVOR to 'gvisor' to use the gVisor-based sandbox, which provides a secure isolation. Ensure that the container and server environment are configured to support sandboxing properly, including enabling SYS_PTRACE capability if required. Also, review and restrict access to the Grist server to trusted users and networks to reduce risk. [1, 2]

Useful 0 Not Useful 0

Compliance Impact

This vulnerability allows execution of arbitrary processes on the server hosting Grist, potentially leading to unauthorized access, modification, or disruption of sensitive data. Such impacts on confidentiality, integrity, and availability could result in non-compliance with data protection regulations like GDPR and HIPAA, which require safeguarding personal and sensitive information against unauthorized access and ensuring system integrity and availability. [2]

Useful 0 Not Useful 0