Once triggered, the affected per-stream receive thread enters a state of approximately 100% CPU usage. Because the process stops responding to standard control-channel termination signals, the server becomes permanently unusable for new connections or existing streams until the process is manually terminated using a SIGKILL signal. This issue is particularly impactful for network performance monitoring infrastructure that relies on iperf3 for capacity testing. Defenders should upgrade to iperf3 version 3.22 or later to mitigate this risk.

Impact

The vulnerability results in a complete service denial for the targeted iperf3 instance. Because the process enters a hang state that does not respond to standard signals, recovery requires manual administrative intervention (SIGKILL). This impacts all network sectors and environments utilizing iperf3 for throughput testing and network diagnostic verification.

Recommendation

• Upgrade all instances of iperf3 to version 3.22 or later to remediate CVE-2026-102253.
• Implement network-level access control lists (ACLs) to restrict access to the iperf3 control channel (default port 5201) to authorized management subnets only.
• Monitor server CPU utilization for prolonged spikes reaching 100% on a single thread associated with the iperf3 process name as an indicator of an active DoS event.