Executive Summary

CVE-2026-7590 is a command injection vulnerability in the Branch Monkey project, specifically in the Preview Endpoint's handling of the dev_script parameter.

The vulnerability occurs because the dev_script argument is executed via the system shell with shell=True in subprocess.Popen(), allowing attackers to inject arbitrary OS commands.

The endpoint validates only the existence of a local Git repository path and commit SHA but does not restrict the commands themselves, enabling remote attackers to execute malicious commands on the server.

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Impact Analysis

This vulnerability can have a high impact on confidentiality, integrity, and availability of the affected system.

• Attackers can read local secrets and sensitive information.
• They can modify or delete files, potentially altering or destroying important data.
• Attackers can disrupt services by executing arbitrary commands, causing denial of service or other operational issues.

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Detection Guidance

This vulnerability can be detected by monitoring and analyzing requests to the `/api/local-claude/time-machine/preview` endpoint, specifically looking for suspicious or unexpected values in the `dev_script` parameter that might contain shell metacharacters or command injection attempts.

Since the vulnerability involves execution of OS commands via subprocess with shell=True, detection can include searching for unusual file creations or processes spawned by the application, such as the creation of files like `/tmp/codex_cmdi_poc` as demonstrated in the proof of concept.

Suggested commands to detect exploitation attempts include:

• Use network monitoring tools (e.g., tcpdump, Wireshark) to capture HTTP requests to the vulnerable endpoint and inspect the `dev_script` parameter.
• On the server, run commands to detect suspicious files or processes, for example: `ls -l /tmp/codex_cmdi_poc` to check for proof-of-concept file creation.
• Use process monitoring commands like `ps aux | grep branch_monkey_mcp` to identify unexpected subprocesses spawned by the application.
• Search application logs for unusual or malformed `dev_script` parameter values.

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Mitigation Strategies

Immediate mitigation steps include removing or disabling the use of shell execution (`shell=True`) in the subprocess calls that handle the `dev_script` parameter.

Replace shell-based command execution with argv list invocation to avoid shell interpretation of input.

Implement an allowlist of permitted commands or inputs for the `dev_script` parameter to restrict what can be executed.

Add regression tests to detect and prevent command injection attempts involving metacharacters.

Monitor and restrict access to the vulnerable endpoint to trusted users or networks until a patch is applied.

If possible, update to a fixed version of the software once available.

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Compliance Impact

The vulnerability allows remote OS command injection, which can lead to unauthorized access, modification, or disruption of data and services. This poses significant risks to confidentiality, integrity, and availability of data.

Such risks can impact compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive data and prevention of unauthorized access or data breaches.

Specifically, the ability for attackers to read local secrets or modify files could lead to exposure or alteration of personal or protected health information, violating regulatory requirements.

Therefore, without proper mitigation, this vulnerability could result in non-compliance with these standards due to potential data breaches and insufficient security controls.

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