CVE-2025-54349 is a medium-severity vulnerability identified in the iperf3 network performance measurement tool, specifically in versions prior to 3.19.1. The vulnerability arises from an off-by-one error (classified as CWE-193) in the iperf_auth.c source file, which leads to a heap-based buffer overflow. An off-by-one error typically occurs when a program writes data just outside the boundary of a buffer by one byte, which in this case corrupts adjacent heap memory. This heap overflow can potentially be exploited by a remote attacker to cause memory corruption, leading to denial of service or possibly limited code execution. The vulnerability is remotely exploitable over the network (Attack Vector: Network) without requiring any privileges or user interaction, but the attack complexity is high, indicating that exploitation requires specific conditions or expertise. The scope is changed, meaning the vulnerability can affect components beyond the initially vulnerable code, and the impact affects confidentiality, integrity, and availability at a low level. No known exploits are currently reported in the wild, and no official patch links are provided yet. The vulnerability was published on August 3, 2025, and is tracked under CWE-193 (Off-by-one Error).

For European organizations, the impact of this vulnerability depends on the extent to which iperf3 is used within their network infrastructure. iperf3 is widely employed for network performance testing and bandwidth measurement, often in enterprise, academic, and telecommunication environments. Exploitation could allow attackers to disrupt network performance testing activities, potentially causing denial of service conditions or limited data exposure. Although the confidentiality and integrity impacts are rated low, disruption of network diagnostics could hinder incident response and network management operations. Given the vulnerability allows remote exploitation without authentication, attackers could target exposed iperf3 services to degrade network monitoring capabilities. This could be particularly impactful for organizations relying on iperf3 for critical network performance validation, such as ISPs, data centers, and research institutions. However, the high attack complexity and lack of known exploits reduce immediate risk. Organizations with iperf3 deployed in isolated or internal networks face lower risk compared to those exposing iperf3 services to untrusted networks.

European organizations should prioritize upgrading iperf3 to version 3.19.1 or later once available, as this will contain the fix for the off-by-one heap overflow. Until a patch is released, organizations should restrict network access to iperf3 services by implementing strict firewall rules limiting connections to trusted hosts and networks only. Network segmentation can further isolate iperf3 instances from untrusted or public networks. Monitoring network traffic for unusual iperf3 activity can help detect potential exploitation attempts. Additionally, organizations should audit their use of iperf3 to ensure it is not unnecessarily exposed and consider disabling or uninstalling iperf3 on systems where it is not essential. Employing runtime protections such as heap memory protection mechanisms (e.g., ASLR, heap canaries) can reduce exploitation success. Finally, maintain up-to-date intrusion detection signatures that may emerge following public disclosure.