CVE-2025-10735 is a Server-Side Request Forgery (SSRF) vulnerability classified under CWE-918 affecting the WordPress plugin 'Block For Mailchimp – Easy Mailchimp Form Integration' developed by bplugins. This vulnerability exists in all versions up to and including 1.1.12. The flaw resides in the mcbSubmit_Form_Data() function, which processes form submissions. Due to insufficient validation of user-supplied input, unauthenticated attackers can exploit this vulnerability to induce the web application to send HTTP requests to arbitrary internal or external URLs. This is a blind SSRF, meaning the attacker may not directly see the response but can infer information or cause side effects by interacting with internal services. The SSRF can be leveraged to query internal network resources that are otherwise inaccessible externally, potentially exposing sensitive data or enabling further attacks such as internal port scanning, accessing metadata services, or manipulating internal APIs. The vulnerability does not require authentication or user interaction, increasing its risk profile. However, the CVSS score is 4.0 (medium severity) with vector AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N, indicating network attack vector, high attack complexity, no privileges or user interaction required, scope changed, no confidentiality or availability impact but low integrity impact. No known exploits are currently reported in the wild, and no patches have been released yet. The vulnerability affects all versions of the plugin, which is used to integrate Mailchimp forms into WordPress sites, a common CMS platform.

For European organizations, this SSRF vulnerability poses a moderate risk primarily to websites using the vulnerable Mailchimp integration plugin on WordPress. Exploitation could allow attackers to access internal services behind firewalls, potentially exposing sensitive internal APIs, configuration endpoints, or cloud metadata services (e.g., AWS, Azure) that could lead to privilege escalation or data leakage. While the direct impact on confidentiality is rated low, the ability to interact with internal systems can facilitate lateral movement or reconnaissance for more severe attacks. Given the widespread use of WordPress in Europe across industries including e-commerce, media, and government, organizations with insufficient segmentation or internal service protections could be at risk. The vulnerability’s unauthenticated nature means attackers can scan and exploit vulnerable sites en masse. However, the high attack complexity and lack of direct confidentiality or availability impact somewhat limit the immediate damage. Nonetheless, organizations relying on internal APIs or cloud services accessible from their web servers should consider this a significant risk vector.

1. Immediate mitigation involves disabling or removing the vulnerable 'Block For Mailchimp – Easy Mailchimp Form Integration' plugin until a patch is released. 2. Implement strict outbound web request filtering on web servers hosting WordPress sites to restrict HTTP requests to only trusted external endpoints, preventing SSRF exploitation. 3. Use Web Application Firewalls (WAFs) with custom rules to detect and block suspicious SSRF patterns targeting the mcbSubmit_Form_Data() endpoint. 4. Harden internal services by enforcing authentication and network segmentation to minimize the impact if SSRF occurs. 5. Monitor web server logs for unusual outbound requests or repeated access to the vulnerable plugin’s endpoints. 6. Once available, promptly apply vendor patches or updates addressing this vulnerability. 7. Conduct internal audits of WordPress plugins to identify and remediate other potential SSRF or input validation issues. 8. Educate web administrators on the risks of SSRF and the importance of plugin management and timely updates.