CVE-2026-91149

A flaw was found in Cockpit. An unauthenticated remote attacker can exploit this vulnerability by initiating and sustaining numerous simultaneous connections to the cockpit-tls service. This forces the service to create an unbounded number of detached threads, consuming system resources such as memory and file descriptors. The primary consequence is a denial of service (DoS), leading to degradation or complete unavailability of the Cockpit service for legitimate users.

This is an Important denial-of-service flaw in Cockpit, allowing unauthenticated remote attackers to degrade or deny service availability. Exploitation requires network reachability to the Cockpit listener on TCP port 9090, enabling attackers to exhaust system resources by spawning unbounded connection threads. The impact is limited to availability, without affecting confidentiality or integrity.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Restrict network access to the Cockpit listener (TCP port 9090) to trusted management networks or localhost only, using host firewall rules such as firewalld zones or iptables rules that limit which sources may reach port 9090. If remote access to the Cockpit web console is not required, disable the listener entirely with systemctl disable --now cockpit.socket. External connection-rate or concurrency limits in front of TCP port 9090, such as those enforced by a firewall or reverse proxy, further reduce exploitability. Lowering the service's task or file-descriptor ceilings can reduce the blast radius, but does not correct the missing concurrency bound in the cockpit-tls accept path; fixes are being pursued for the affected product streams.