CVE-2025-55279 is a medium-severity vulnerability identified in the ZKTeco WL20 Biometric Attendance System, specifically in firmware versions up to ZLM31-FXO1-3.1.8. The root cause is the presence of a hard-coded private key stored in plaintext within the device's firmware. This key is embedded directly in the binary, making it accessible to an attacker who gains physical access to the device. By extracting and analyzing the firmware, an attacker can retrieve this private key. Possession of the private key enables unauthorized decryption of sensitive data transmitted or stored by the device. Furthermore, it facilitates Man-in-the-Middle (MitM) attacks, allowing interception and manipulation of communications between the device and other systems. The vulnerability does not require network access or user interaction but does require physical access to the device, which limits remote exploitation. The CVSS 4.0 score of 6.9 reflects a medium severity, considering the attack vector is physical (AV:P), with low privileges required (PR:N), no user interaction (UI:N), but high impact on confidentiality and integrity (VC:H, VI:H). No known exploits are currently reported in the wild, and no patches have been published yet. The vulnerability is classified under CWE-798, indicating the use of hard-coded credentials, a common security anti-pattern that significantly weakens device security posture.

For European organizations deploying ZKTeco WL20 biometric attendance systems, this vulnerability poses a tangible risk to the confidentiality and integrity of biometric and attendance data. Unauthorized decryption could expose sensitive personal data of employees, potentially violating GDPR and other data protection regulations. Man-in-the-Middle attacks could allow attackers to manipulate attendance records, leading to fraud or operational disruptions. The requirement for physical access means insider threats or attackers with physical proximity to the devices are the primary risk vectors. In sectors with high security demands such as government, finance, healthcare, and critical infrastructure, exploitation could undermine trust in biometric authentication systems and lead to reputational damage. Additionally, compromised attendance systems could serve as pivot points for broader network infiltration if integrated with enterprise IT infrastructure. The lack of available patches increases the urgency for organizations to implement compensating controls to mitigate risk.

European organizations should immediately inventory all ZKTeco WL20 devices and verify firmware versions. Until a vendor patch is available, physical security must be enhanced to prevent unauthorized access to the devices, including secure mounting, tamper-evident seals, and restricted access areas. Firmware extraction should be deterred by deploying devices in controlled environments with surveillance. Network segmentation should isolate attendance systems from critical IT infrastructure to limit lateral movement in case of compromise. Organizations should monitor network traffic for anomalies indicative of MitM attacks or unauthorized decryption attempts. Where possible, consider replacing affected devices with models that do not contain hard-coded credentials or that have received security updates. Additionally, organizations should engage with ZKTeco for timelines on patch releases and apply updates promptly once available. Employee awareness programs should highlight the risks of physical tampering and encourage reporting of suspicious activity.