CVE-2025-62689 is a heap-based buffer overflow vulnerability identified in GNU libmicrohttpd, a lightweight HTTP server library widely used in embedded systems and applications requiring minimal HTTP server functionality. The vulnerability stems from a NULL pointer dereference condition present in versions 1.0.2 and earlier. An attacker can exploit this flaw by sending a specially crafted network packet to a server or device running the vulnerable libmicrohttpd version. This crafted input triggers the NULL pointer dereference, causing the application to crash and resulting in a denial-of-service (DoS) condition. The vulnerability does not affect confidentiality or integrity but severely impacts availability. Exploitation requires no authentication or user interaction, and the attack vector is network-based, making it remotely exploitable. The vulnerability was addressed in a commit (ff13abc) after the 1.0.2 release, which corrected the pointer handling logic to prevent the dereference. No known exploits have been reported in the wild yet, but the vulnerability’s characteristics make it a credible threat, especially for devices exposed to untrusted networks. The affected library is commonly embedded in IoT devices, telecommunications equipment, and lightweight HTTP servers, increasing the attack surface in these environments. The CVSS v3.0 score of 7.5 reflects the high severity due to ease of exploitation and impact on service availability. Organizations using libmicrohttpd should audit their deployments and apply updates or patches to mitigate this risk.

For European organizations, the primary impact of CVE-2025-62689 is the potential for denial-of-service attacks against systems running vulnerable versions of libmicrohttpd. This can lead to service outages, disruption of critical infrastructure, and loss of availability in embedded devices and lightweight HTTP servers. Sectors such as telecommunications, manufacturing, energy, and IoT device management are particularly vulnerable due to their reliance on embedded HTTP services. Disruptions could affect operational technology environments, customer-facing services, and internal management systems. The lack of confidentiality or integrity impact limits data breach risks, but availability loss can cause significant operational and financial damage. The remote exploitability without authentication increases the threat level, especially for devices exposed to the internet or untrusted networks. European organizations with legacy systems or slow patch cycles are at higher risk. Additionally, denial-of-service conditions in critical infrastructure components could have cascading effects on dependent services and supply chains.

1. Immediately identify all systems and devices using GNU libmicrohttpd version 1.0.2 or earlier within the organization’s network and asset inventory. 2. Apply the patch or update to a libmicrohttpd version that includes the fix implemented after commit ff13abc. If an official patch is not yet available, consider applying the fix manually from the commit or vendor advisories. 3. For embedded devices where updating the library is challenging, implement network-level protections such as firewall rules or intrusion prevention systems to block or limit access to the vulnerable HTTP service from untrusted sources. 4. Monitor network traffic for anomalous or malformed HTTP packets that could indicate exploitation attempts targeting this vulnerability. 5. Employ segmentation to isolate vulnerable devices from critical network segments to reduce potential impact. 6. Coordinate with vendors and suppliers to ensure timely updates and security patches for embedded systems using libmicrohttpd. 7. Incorporate this vulnerability into incident response and vulnerability management workflows to ensure rapid detection and remediation. 8. Conduct penetration testing and vulnerability scanning focused on libmicrohttpd versions to proactively identify exposure.