CVE-2026-59845 Red Hat CVE debrief

Who should care

Users of libssh who utilize the ProxyCommand feature should verify their configurations and ensure that proper error handling is in place to mitigate potential denial of service attacks. System administrators and security teams responsible for libssh deployments should review their configurations and implement necessary mitigations.

Technical summary

The vulnerability exists in libssh when the ProxyCommand feature is used. An unchecked fork() failure can result in a process ID of -1 being stored. During the cleanup process, signals can be sent to the caller's accessible process tree, potentially leading to a local denial of service. The CVSS score for this vulnerability is 5.3, classified as MEDIUM severity. Users of libssh who utilize the ProxyCommand feature should verify their configurations and ensure that proper error handling is in place to mitigate potential denial of service attacks.

Defensive priority

Medium priority due to potential for local denial of service. Ensure systems using libssh with ProxyCommand are reviewed and updated. Implement additional monitoring for unusual system activity and conduct regular security audits.

Recommended defensive actions

• Verify libssh configurations for proper error handling
• Update libssh to the latest version
• Review system configurations for potential vulnerabilities
• Implement additional monitoring for unusual system activity
• Conduct regular security audits
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

Evidence is based on information from the NVD and CVE records. Further analysis and verification are recommended to fully understand the scope and impact of this vulnerability. The vulnerability exists in libssh when the ProxyCommand feature is used. An unchecked fork() failure can result in a process ID of -1 being stored. During the cleanup process, signals can be sent to the caller's accessible process tree, potentially leading to a local denial of service. Users of libssh who utilize the ProxyCommand feature should verify their configurations and ensure that proper error handling is in place to mitigate potential denial of service attacks.

Official resources