CVE-2026-21966 is a vulnerability identified in Oracle Hospitality OPERA 5 Property Services, a widely used property management system in the hospitality industry. The affected versions include 5.6.19.23, 5.6.25.17, 5.6.26.10, and 5.6.27.4. The vulnerability allows an unauthenticated attacker with network access over HTTP to compromise the system by exploiting a flaw that enables unauthorized read and write operations on accessible data. Specifically, attackers can perform unauthorized update, insert, or delete actions, as well as read access to a subset of data. The attack requires human interaction from a user other than the attacker, indicating a social engineering component or tricking a legitimate user into performing an action that facilitates exploitation. The vulnerability has a CVSS 3.1 base score of 6.1, reflecting low attack complexity (AC:L), no privileges required (PR:N), network attack vector (AV:N), and user interaction required (UI:R). The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component, potentially impacting additional Oracle Hospitality products. The confidentiality and integrity impacts are low but present, while availability is unaffected. No known exploits have been reported in the wild, but the ease of exploitation and potential impact on sensitive hospitality data make this a significant concern. The vulnerability highlights risks in property management systems that handle guest data, reservations, and financial transactions, which are critical for hospitality operations.

For European organizations, especially those in the hospitality sector using Oracle Hospitality OPERA 5, this vulnerability could lead to unauthorized access and manipulation of sensitive guest and operational data. Confidentiality breaches could expose personal guest information, while integrity compromises could result in altered reservation details, billing information, or operational data, potentially disrupting business processes and damaging reputation. Although availability is not impacted, the unauthorized data modifications could cause operational inefficiencies and financial losses. The requirement for human interaction suggests phishing or social engineering could be vectors, increasing risk in environments with less user security awareness. The scope change indicates that exploitation could affect other integrated Oracle Hospitality products, broadening the impact. European hospitality organizations are often subject to strict data protection regulations such as GDPR, so data breaches could also result in regulatory penalties and legal consequences. The vulnerability's network accessibility via HTTP increases exposure, especially if systems are accessible from less secure networks or the internet. Overall, the threat could undermine trust in hospitality services and lead to financial and reputational damage.

1. Apply official patches or updates from Oracle as soon as they become available for the affected OPERA 5 versions to remediate the vulnerability. 2. Restrict network access to Oracle Hospitality OPERA 5 Property Services interfaces, limiting exposure to trusted internal networks and blocking unnecessary HTTP access from external or untrusted sources. 3. Implement strict network segmentation to isolate OPERA 5 systems from general corporate networks and the internet. 4. Enhance user awareness training focused on social engineering and phishing risks, emphasizing caution when interacting with unexpected requests or links, as exploitation requires human interaction. 5. Monitor logs and network traffic for unusual activities indicative of exploitation attempts, such as unauthorized data modification or access patterns. 6. Employ multi-factor authentication (MFA) where possible on systems interacting with OPERA 5 to reduce the risk of unauthorized access. 7. Conduct regular security assessments and penetration testing on hospitality systems to identify and remediate other potential vulnerabilities. 8. Review and tighten access controls within OPERA 5 to ensure least privilege principles are enforced, minimizing the impact of any unauthorized access. 9. Maintain an incident response plan tailored to hospitality sector threats, enabling rapid containment and recovery if exploitation occurs.