CVE-2025-27453 identifies a vulnerability in the Endress+Hauser MEAC300-FNADE4 device, specifically related to the handling of the PHPSESSION cookie. The vulnerability arises because the HttpOnly flag is not set on this sensitive cookie, allowing client-side scripts such as JavaScript to access it. The HttpOnly attribute is a security measure that prevents cookies from being accessed via client-side scripting, thereby mitigating the risk of cookie theft through cross-site scripting (XSS) or other injection attacks. Without this flag, malicious scripts running in the context of the affected web application can read the session cookie, potentially leading to session hijacking or impersonation of legitimate users. The CVSS v3.1 base score is 5.3, indicating a medium severity level. The vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N) reveals that the attack is network-based (AV:N), requires high attack complexity (AC:H), no privileges (PR:N), but does require user interaction (UI:R). The impact is limited to confidentiality (C:H), with no impact on integrity or availability. The vulnerability affects version 0 of the product, which likely refers to initial or specific firmware/software versions. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability is classified under CWE-1004, which corresponds to sensitive cookies without the HttpOnly flag, a common web security misconfiguration.

For European organizations using the Endress+Hauser MEAC300-FNADE4 device, this vulnerability poses a risk primarily to the confidentiality of session information. If exploited, attackers could steal session cookies via malicious scripts, potentially gaining unauthorized access to the device's web interface or management console. This could lead to unauthorized monitoring or manipulation of industrial processes controlled by the device, especially in critical infrastructure sectors such as manufacturing, utilities, or chemical processing. Although the vulnerability does not directly affect integrity or availability, unauthorized access could indirectly lead to operational disruptions or data leakage. The requirement for user interaction and high attack complexity somewhat limits the risk, but targeted spear-phishing or social engineering attacks could facilitate exploitation. Given the industrial nature of the product, the impact on operational technology (OT) environments could be significant if attackers leverage this vulnerability as a foothold for further attacks.

To mitigate this vulnerability, organizations should first verify if their Endress+Hauser MEAC300-FNADE4 devices are running affected versions. Since no official patches are currently available, immediate mitigation steps include: 1) Restricting access to the device's web interface to trusted networks and users only, using network segmentation and firewall rules to limit exposure. 2) Implementing web application firewalls (WAFs) that can detect and block malicious scripts attempting to access cookies. 3) Encouraging users to avoid interacting with suspicious links or content that could trigger malicious scripts. 4) Monitoring device logs and network traffic for unusual access patterns or attempts to exploit session cookies. 5) Contacting Endress+Hauser support for any available firmware updates or security advisories addressing this issue. 6) If feasible, configuring the device or its web server to set the HttpOnly flag on session cookies manually, or applying custom security controls to enforce this behavior. 7) Employing multi-factor authentication (MFA) on management interfaces to reduce the risk of session hijacking leading to unauthorized access.