CVE-2025-53007 is a high-severity vulnerability affecting the arduino-esp32 project, which provides an Arduino core for the ESP32 microcontroller platform. The vulnerability is classified under CWE-113, indicating improper neutralization of CRLF (Carriage Return Line Feed) sequences in HTTP headers, commonly known as HTTP Response Splitting. Specifically, the issue resides in the `sendHeader` function, which constructs HTTP response headers by concatenating arbitrary input for the header name and value without any validation or sanitization. This lack of input sanitization allows an attacker who can control the inputs to inject CR (`\r`) or LF (`\n`) characters into the header name or value. By doing so, the attacker can manipulate the HTTP response structure, injecting additional headers or even an entirely new HTTP response. This can lead to various HTTP protocol attacks such as cache poisoning, cross-site scripting (XSS), session fixation, or other header injection attacks. The vulnerability affects versions prior to 3.3.0-RC1 and 3.2.1, with fixes introduced in versions 3.3.0-RC1 and 3.2.1. The CVSS 4.0 score is 8.9 (high), reflecting the vulnerability's network attack vector, low complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability. No known exploits are currently reported in the wild, but the potential for exploitation is significant given the nature of the vulnerability and the widespread use of ESP32 devices in IoT and embedded applications. Attackers exploiting this vulnerability could manipulate HTTP responses to deceive clients or intermediaries, potentially leading to data leakage, session hijacking, or denial of service.

For European organizations, the impact of this vulnerability can be substantial, especially for those deploying ESP32-based devices in critical infrastructure, industrial control systems, smart building management, or consumer IoT products. Exploitation could allow attackers to manipulate HTTP responses from these devices, leading to unauthorized access, data interception, or disruption of services. Given the increasing adoption of ESP32 modules in smart city applications, healthcare devices, and manufacturing automation across Europe, successful exploitation could compromise sensitive data or disrupt operational continuity. Additionally, HTTP response splitting can facilitate further attacks such as cache poisoning or cross-site scripting, which could affect web applications interfacing with these devices. The vulnerability's network-exploitable nature means attackers do not need physical access or authentication, increasing the risk of remote compromise. This is particularly concerning for European organizations subject to stringent data protection regulations like GDPR, where data breaches or service disruptions could result in significant legal and financial penalties.

European organizations should take the following specific mitigation steps: 1) Immediately identify and inventory all ESP32 devices running vulnerable versions of arduino-esp32 firmware. 2) Upgrade all affected devices to arduino-esp32 versions 3.3.0-RC1 or 3.2.1 or later, where the vulnerability is patched. 3) If firmware upgrades are not immediately feasible, implement network-level protections such as web application firewalls (WAFs) or intrusion prevention systems (IPS) configured to detect and block HTTP header injection patterns, including CRLF sequences. 4) Employ strict input validation and sanitization on any user-controllable inputs that may be passed to the `sendHeader` function or similar HTTP header construction routines in custom firmware. 5) Monitor network traffic for anomalous HTTP responses that may indicate exploitation attempts, including unexpected header structures or duplicated HTTP responses. 6) For critical deployments, consider segmenting ESP32 devices on isolated network segments with limited external access to reduce exposure. 7) Engage with device manufacturers or vendors to ensure timely firmware updates and security patches. 8) Incorporate this vulnerability into incident response and vulnerability management workflows to ensure rapid detection and remediation.