CVE-2025-62689 is a heap-based buffer overflow vulnerability identified in the GNU Project's libmicrohttpd library, specifically affecting versions 1.0.2 and earlier. The root cause is a NULL pointer dereference triggered by processing specially crafted network packets, which can cause the affected application to crash, resulting in a denial-of-service (DoS) condition. This vulnerability does not require any authentication or user interaction, and the attack vector is network-based, meaning an attacker can exploit it remotely with low complexity. The vulnerability was addressed in a commit (ff13abc) after the 1.0.2 release, indicating that users running the latest master branch or versions beyond 1.0.2 are not vulnerable. libmicrohttpd is a small C library used to embed HTTP server functionality into applications, commonly found in embedded systems, network appliances, and various GNU/Linux-based software stacks. The CVSS v3.0 base score of 7.5 reflects the high severity due to the potential for complete service disruption (availability impact), although confidentiality and integrity remain unaffected. No public exploits or active exploitation have been reported yet, but the ease of exploitation and network exposure make it a critical issue to address. The vulnerability’s impact is primarily on availability, as successful exploitation leads to application crashes and service outages, which could affect dependent services and systems.

For European organizations, the primary impact of CVE-2025-62689 is the potential for denial-of-service attacks against applications or devices embedding vulnerable versions of libmicrohttpd. This can disrupt critical services, particularly in sectors relying on embedded HTTP servers such as telecommunications, industrial control systems, IoT devices, and network infrastructure. Service outages could lead to operational downtime, loss of productivity, and potential cascading effects if the affected systems are part of larger service delivery chains. Although the vulnerability does not compromise confidentiality or integrity, the availability impact alone can be significant, especially for critical infrastructure and public-facing services. Organizations with extensive GNU/Linux deployments or custom applications embedding libmicrohttpd are at risk. The lack of required authentication and the remote attack vector increase the threat level, as attackers can exploit the vulnerability without prior access or user interaction. This could also facilitate further attacks by causing disruptions that distract or degrade defensive capabilities.

1. Immediately upgrade libmicrohttpd to a version that includes the fix introduced after commit ff13abc, ensuring no vulnerable versions remain in your environment. 2. If upgrading is not immediately feasible, apply any available backported patches or mitigations from trusted sources. 3. Conduct an inventory of all systems and applications embedding libmicrohttpd to identify vulnerable instances, including embedded devices and network appliances. 4. Implement network-level protections such as intrusion detection/prevention systems (IDS/IPS) to monitor and block suspicious or malformed HTTP traffic targeting libmicrohttpd services. 5. Employ strict network segmentation to limit exposure of vulnerable services to untrusted networks, reducing the attack surface. 6. Monitor application logs and system behavior for signs of crashes or unusual HTTP request patterns indicative of exploitation attempts. 7. Engage with vendors and open-source communities to stay informed about patches, advisories, and best practices related to libmicrohttpd. 8. Develop incident response plans that include procedures for handling DoS conditions caused by this vulnerability to minimize downtime.