CVE-2023-37749 is a security vulnerability identified in HubSpot's REST API, specifically in version v1.29441, where incorrect access control allows unauthenticated attackers to retrieve user data without proper authorization. The vulnerability arises from a failure to enforce authentication and authorization checks on a REST API endpoint, effectively exposing sensitive user information to anyone who can reach the endpoint. This type of flaw is critical because REST APIs often serve as gateways to backend systems and data repositories. The absence of authentication means that attackers do not need valid credentials or user interaction to exploit the vulnerability, significantly lowering the barrier to attack. Although no public exploits have been reported yet, the potential for data leakage is substantial, especially considering HubSpot's widespread use in customer relationship management (CRM) and marketing automation. The vulnerability was reserved in July 2023 and published in October 2025, but no CVSS score or patch information is currently available, indicating that remediation guidance may still be pending. The lack of patch links suggests that organizations must proactively implement compensating controls to mitigate risk. This vulnerability primarily threatens confidentiality, as unauthorized data access can lead to information disclosure, privacy violations, and potential compliance breaches.

For European organizations, the impact of CVE-2023-37749 could be severe, particularly for those relying on HubSpot for managing customer data, marketing campaigns, and internal user information. Unauthorized access to user data can result in data breaches exposing personally identifiable information (PII), leading to regulatory penalties under GDPR and reputational damage. The exposure of sensitive user details could facilitate further attacks such as phishing, social engineering, or identity theft. Additionally, compromised data integrity and loss of trust in digital services may disrupt business operations and client relationships. Since the vulnerability requires no authentication, attackers can exploit it remotely and anonymously, increasing the risk of widespread abuse. The absence of known exploits in the wild does not diminish the urgency, as threat actors may develop exploits rapidly once details become public. Organizations in sectors with strict data protection requirements, such as finance, healthcare, and telecommunications, are particularly vulnerable to the consequences of such data leaks.

To mitigate CVE-2023-37749, European organizations using HubSpot should immediately audit their API configurations and access controls. They should restrict API endpoint exposure by implementing network-level controls such as IP whitelisting and firewall rules to limit access to trusted sources. Enforce strong authentication and authorization mechanisms on all API endpoints, including the use of OAuth tokens or API keys with minimal privileges. Monitor API usage logs for anomalous or unauthorized access patterns that could indicate exploitation attempts. Engage with HubSpot support to obtain official patches or updates addressing the vulnerability and apply them promptly once available. Until a patch is released, consider disabling or limiting the vulnerable API endpoints if feasible. Conduct regular security assessments and penetration testing focused on API security to detect similar issues proactively. Additionally, ensure that incident response plans include procedures for handling potential data breaches resulting from API vulnerabilities.