# CVE-2026-102253: iperf3 denial of service in UDP receive worker

Source: https://junglewise.ai/threats/cve-2026-102253-iperf3-versions-prior-to-3-22-contains-a-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-29. Updated: 2026-09-29  
License: CC BY 4.0 with a link back

CVE-2026-102253 · Severity: high · CVSS 7.5 · Published 2026-09-29

iperf3 is a network bandwidth measurement tool used to test network performance. An unauthenticated remote attacker can crash the iperf3 server by sending a specially crafted control message and UDP packet, causing the server to enter an infinite loop and become unresponsive. The server will consume 100% CPU and require forcible termination, making it unusable for network testing until manually restarted.

Technologies: [ESnet Iperf3](https://junglewise.ai/threats/technologies/esnet-iperf3). Vendors: [ESnet](https://junglewise.ai/threats/vendors/esnet).

## Quick answers

**Is CVE-2026-102253 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-102253 being exploited in the wild.

**How severe is CVE-2026-102253?** High severity, with a CVSS score of 7.5, published 29 September 2026.

**Which products and versions are affected?** ESnet Iperf3 prior to 3.22.

**Is there a fix for CVE-2026-102253?** A patch was published on 2026-09-29: Version 3.22 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-102253 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-102253?** Check whether you run ESnet Iperf3 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in iperf3's UDP receive worker thread, where a crafted control-channel parameter message followed by a 16-byte UDP datagram triggers an infinite loop. This is a remotely exploitable denial of service requiring no authentication or user interaction. The affected per-stream receive thread pins at approximately 100% CPU usage and does not respond to normal control-channel closure signals, requiring a SIGKILL to terminate the process.

## Affected products

- ESnet iperf3 prior to 3.22

## Timeline

- 2026-09-29: disclosed
- 2026-09-29: patched: Version 3.22 released

## References

- [https://github.com/esnet/iperf/blob/master/RELNOTES.md](https://github.com/esnet/iperf/blob/master/RELNOTES.md)
- [https://github.com/esnet/iperf/releases/tag/3.22](https://github.com/esnet/iperf/releases/tag/3.22)

## Related threats

- [iperf3 heap buffer overflow in RSA decryption](https://junglewise.ai/threats/cve-2026-101283-iperf3-3-20-3-21-esnet-iperf-has-a-pre-auth-heap-buffer-overflow)
- [iperf3 heap use-after-free in server watchdog timer](https://junglewise.ai/threats/cve-2026-101276-iperf3-3-21-esnet-iperf-contains-a-remote-unauthenticated-heap)