CVE-2025-55763 is a buffer overflow vulnerability found in the URI parser component of CivetWeb versions 1.14 through 1.16, which are the latest versions at the time of disclosure. CivetWeb is an embedded web server widely used in IoT devices, embedded systems, and lightweight web applications. The vulnerability arises during the processing of HTTP requests, where a specially crafted URI can overflow the buffer allocated for parsing. This overflow corrupts heap memory, which can lead to denial of service (DoS) conditions or enable an attacker to execute arbitrary code remotely. Because the flaw is triggered by a remote HTTP request, exploitation does not require prior authentication or user interaction, making it a critical remote code execution (RCE) vector. The absence of a CVSS score indicates that the vulnerability is newly disclosed and not yet fully scored, but the technical details suggest a high severity due to the potential for full system compromise. No known exploits are currently reported in the wild, and no official patches or mitigations have been published at the time of disclosure. The vulnerability affects all deployments running the vulnerable CivetWeb versions, which are commonly embedded in various networked devices and applications, increasing the attack surface significantly.

For European organizations, the impact of CVE-2025-55763 could be substantial, especially for those relying on embedded systems, IoT devices, or custom applications using CivetWeb as their web server component. Successful exploitation could lead to remote code execution, allowing attackers to gain control over affected devices or applications. This could result in data breaches, disruption of critical services, or use of compromised devices as footholds for lateral movement within networks. Industries such as manufacturing, healthcare, telecommunications, and critical infrastructure, which often deploy embedded systems and IoT devices, are particularly at risk. The potential for denial of service also threatens availability, which could disrupt business operations or critical services. Given the remote and unauthenticated nature of the exploit, attackers could target vulnerable systems at scale, increasing the risk of widespread impact across European enterprises and public sector organizations.

Organizations should immediately inventory their environments to identify any use of CivetWeb versions 1.14 through 1.16. Given the lack of official patches, temporary mitigations include implementing network-level protections such as web application firewalls (WAFs) configured to detect and block malformed HTTP requests targeting URI parsing. Restricting external access to devices running CivetWeb and segmenting networks to isolate vulnerable systems can reduce exposure. Monitoring network traffic for unusual HTTP requests and enabling detailed logging on affected devices will aid in early detection of exploitation attempts. Organizations should also engage with vendors or developers of embedded devices and applications using CivetWeb to obtain or request patches or updates. Once patches become available, prompt application is critical. Additionally, applying runtime protections such as heap memory protection mechanisms or using compiler-based mitigations (e.g., stack canaries, ASLR) in custom builds can reduce exploitation risk.