CVE-2025-62236 is a vulnerability classified under CWE-204 (Observable Response Discrepancy) affecting the Frontier Airlines website flyfrontier.com. The issue arises from a publicly accessible endpoint that validates whether an email address is associated with an existing user account. Because the endpoint provides different responses based on the validity of the email address, an unauthenticated remote attacker can enumerate valid email accounts by submitting various email addresses and observing the responses. This form of user enumeration does not require any authentication or user interaction, making it trivially exploitable over the network. The vulnerability has a CVSS 3.1 base score of 5.3, reflecting a medium severity level, primarily due to its impact on confidentiality (limited to disclosure of valid emails) without affecting integrity or availability. No known exploits have been reported in the wild, and no patches have been published as of the vulnerability disclosure date. The flaw can be leveraged by attackers to facilitate targeted phishing, credential stuffing, or social engineering attacks by confirming valid user identifiers. The lack of rate limiting or uniform error messages likely contributes to the ease of exploitation. This vulnerability highlights the importance of designing authentication-related endpoints to avoid revealing user existence information through response discrepancies.

For European organizations, the primary impact of CVE-2025-62236 lies in the increased risk of targeted phishing and social engineering attacks. If employees or customers use email addresses registered with Frontier Airlines, attackers can confirm valid accounts and craft more convincing spear-phishing campaigns, potentially leading to credential compromise or unauthorized access to corporate resources. Although the vulnerability does not directly compromise systems or data, it lowers the barrier for attackers to identify valid targets, increasing the likelihood of successful subsequent attacks. Organizations involved in travel, logistics, or with employees frequently traveling to or from the US may be more exposed. Additionally, this vulnerability could affect customer trust and brand reputation if exploited in broader attack campaigns. The lack of direct integrity or availability impact means operational disruption is unlikely, but the confidentiality impact on user identity information is non-negligible. European data protection regulations such as GDPR may also consider the exposure of personal data (email addresses) as a privacy concern requiring mitigation.

To mitigate CVE-2025-62236, Frontier Airlines should implement uniform response messages for email validation endpoints to prevent attackers from distinguishing valid from invalid email addresses. Rate limiting and IP throttling should be applied to reduce the feasibility of automated enumeration attacks. Implementing CAPTCHA challenges after a threshold of failed validation attempts can further hinder automated abuse. Monitoring and alerting on unusual patterns of email validation requests can help detect enumeration attempts early. Organizations should educate employees about phishing risks and encourage the use of multi-factor authentication to reduce the impact of credential compromise. European organizations should review their exposure by identifying employees or customers with Frontier Airlines accounts and consider additional email filtering or threat intelligence integration to detect phishing campaigns leveraging enumerated emails. Finally, Frontier Airlines should prioritize releasing a patch or update to address this vulnerability and communicate transparently with affected users.