libssh ProxyCommand Local Denial of Service

Executive Summary

This vulnerability is in libssh where ProxyCommand is used. If fork() fails, it returns -1 which is stored as a process ID. During cleanup, signals may be sent to unintended processes, causing a local denial of service.

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Detection Guidance

Check if libssh is installed and ProxyCommand is configured in SSH client configurations. Look for processes using libssh with ProxyCommand settings. Commands like 'ps aux | grep ssh' or 'ss -tulnp | grep ssh' may help identify active SSH sessions.

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Impact Analysis

It can cause a local denial of service by disrupting processes in your system if ProxyCommand is used with libssh. This may lead to system instability or unresponsiveness.

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Compliance Impact

This vulnerability primarily causes a local denial of service by sending signals across the caller's process tree due to improper fork() failure handling. It does not directly impact data confidentiality or integrity, which are key concerns for GDPR or HIPAA. However, a denial of service could indirectly affect compliance by disrupting services handling sensitive data.

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Mitigation Strategies

Update libssh to the latest patched version. Disable ProxyCommand in SSH client configurations if not required. Monitor system logs for unusual signal-related activities or process tree modifications.

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