Vendure is an open-source headless commerce platform widely used for building e-commerce backends. The vulnerability identified as CVE-2026-25050 affects the NativeAuthenticationStrategy.authenticate() method in Vendure versions prior to 3.5.3. The method is vulnerable to a timing attack that enables an attacker to enumerate valid usernames (typically email addresses) by exploiting the difference in response times when authenticating. Specifically, when a user is not found in the database, the method returns immediately, resulting in a fast response (~1-5ms). However, when a user exists, the method performs bcrypt password hash verification, which takes significantly longer (~200-400ms). This timing discrepancy allows an attacker to distinguish between valid and invalid usernames by measuring response times over multiple authentication attempts. The vulnerability is classified under CWE-202 (Exposure of Sensitive Information Through Data Queries). Although the CVSS 4.0 base score is low (2.7) due to the lack of direct impact on confidentiality, integrity, or availability and no need for authentication or user interaction, the information disclosure can facilitate further attacks such as credential stuffing, phishing, or social engineering. The issue was addressed and fixed in Vendure version 3.5.3 by normalizing response times to prevent timing-based enumeration. No known exploits are currently reported in the wild.

For European organizations using vulnerable versions of Vendure, this vulnerability can lead to the exposure of valid usernames, which are often email addresses. While this does not directly compromise passwords or system integrity, it provides attackers with a verified list of user accounts, significantly lowering the barrier for targeted phishing campaigns, credential stuffing attacks, and social engineering. This can result in unauthorized access if users reuse passwords or fall victim to phishing. E-commerce platforms are high-value targets due to the sensitive customer data and financial transactions involved. The exposure of usernames can also damage customer trust and lead to regulatory scrutiny under GDPR, especially if combined with other vulnerabilities or data breaches. The low CVSS score does not diminish the practical risk posed by information disclosure in the context of layered attacks.

The primary mitigation is to upgrade Vendure to version 3.5.3 or later, where the timing attack has been fixed by equalizing response times regardless of user existence. For organizations unable to upgrade immediately, consider implementing application-layer mitigations such as introducing artificial delays on authentication failures to normalize response times, or using rate limiting and IP reputation filtering to reduce the feasibility of timing attacks. Monitoring authentication logs for anomalous patterns indicative of enumeration attempts is recommended. Additionally, enforce strong password policies and multi-factor authentication (MFA) to reduce the impact of username enumeration. Educate users about phishing risks and monitor for phishing campaigns targeting your user base. Finally, ensure that logging and alerting mechanisms are in place to detect suspicious authentication activity.