Authenticated Remote Code Execution in OpenBullet2

Compliance Impact

The vulnerability in OpenBullet2 allows authenticated users to execute arbitrary code on the server, potentially leading to unauthorized access to sensitive data and system resources.

Such unauthorized access and control could result in violations of data protection regulations like GDPR and HIPAA, which mandate strict controls over access to personal and sensitive information.

Exploitation of this vulnerability could compromise confidentiality, integrity, and availability of data, thereby impacting compliance with these standards.

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Executive Summary

CVE-2026-25856 is an authenticated remote code execution vulnerability in OpenBullet2 versions up to 0.3.2. It allows authenticated users to execute arbitrary C# code on the server by creating or modifying job configurations.

The vulnerability exists because the plain C# execution mode does not have proper reference filtering or API restrictions, which enables attackers to access the file system, spawn processes, and invoke arbitrary .NET APIs with the privileges of the running process.

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Impact Analysis

This vulnerability can have a significant impact as it allows an authenticated attacker to execute arbitrary code on the server hosting OpenBullet2.

• Attackers can access and manipulate the file system.
• They can spawn new processes on the server.
• They can invoke any .NET APIs available to the process user, potentially leading to full system compromise.

Because the attacker operates with the privileges of the running process, the impact can be severe, including data theft, service disruption, or further network compromise.

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Mitigation Strategies

To mitigate this vulnerability, you should upgrade OpenBullet2 to a version later than 0.3.2 where this issue is fixed.

Since the vulnerability allows authenticated users to execute arbitrary C# code via job configurations, restricting access to trusted users and limiting permissions of the OpenBullet2 process can reduce risk.

Avoid using the plain C# execution mode or apply additional controls to restrict code execution if possible.

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Detection Guidance

This vulnerability requires authenticated access to OpenBullet2 version 0.3.2 or earlier to exploit the remote code execution via job configuration modifications.

To detect if your system is vulnerable, first verify the OpenBullet2 version running on your server. If it is version 0.3.2 or earlier, it is susceptible.

Since the vulnerability involves authenticated users executing arbitrary C# code through job configurations, detection involves checking for unauthorized or suspicious job configuration changes or unusual process spawning on the server.

Suggested commands to help detect potential exploitation or presence of the vulnerable version include:

• Check the OpenBullet2 version by inspecting the application files or querying the application endpoint if available.
• Monitor server logs for unusual job configuration changes or API calls related to job creation/modification.
• On the server, use commands to detect suspicious processes or file system changes, for example:
• Linux: `ps aux | grep dotnet` to find unexpected .NET processes.
• Linux: `find /path/to/openbullet2/jobs -type f -mtime -1` to find recently modified job configuration files.
• Windows: Use PowerShell commands like `Get-Process` to identify unusual processes spawned by OpenBullet2.
• Review application logs for any execution of arbitrary C# code or errors related to job configurations.

Note that no specific detection commands or signatures are provided in the available resources, so monitoring for suspicious activity and verifying the version is the primary method.

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