CVE-2025-10735 is a Blind Server-Side Request Forgery (SSRF) vulnerability classified under CWE-918, found in the 'Block For Mailchimp – Easy Mailchimp Form Integration' WordPress plugin maintained by bplugins. The vulnerability affects all versions up to and including 1.1.12 and resides in the mcbSubmit_Form_Data() function. SSRF vulnerabilities allow attackers to abuse the server to send HTTP requests to arbitrary destinations, including internal network services that are otherwise inaccessible externally. This particular flaw is 'blind', meaning the attacker does not receive direct response data from the internal requests, but can infer success or failure through side effects or timing. The vulnerability requires no authentication and no user interaction, but has a high attack complexity, likely due to the need to craft specific requests or conditions to exploit it effectively. The CVSS v3.1 base score is 4.0 (medium severity), reflecting no confidentiality impact, limited integrity impact, and no availability impact. The scope is changed (S:C), indicating the vulnerability affects resources beyond the vulnerable component itself. Although no public exploits have been reported, the vulnerability could be leveraged for internal network reconnaissance, accessing metadata services, or interacting with internal APIs, potentially leading to further compromise. The plugin is widely used for integrating Mailchimp forms into WordPress sites, which are common in marketing and customer engagement. The lack of available patches at the time of publication increases the urgency for mitigation. The vulnerability's exploitation could allow attackers to bypass perimeter defenses and interact with internal services, posing a risk especially in segmented or cloud environments where internal services hold sensitive data or control functions.

For European organizations, this SSRF vulnerability presents a risk of unauthorized internal network access originating from compromised WordPress servers. Attackers could leverage this to scan internal services, access metadata endpoints (such as cloud instance metadata), or interact with internal APIs that are not exposed externally. This could lead to information disclosure, limited data manipulation, or serve as a foothold for lateral movement within the network. Organizations relying on WordPress sites with this plugin, especially those integrating Mailchimp forms for marketing or customer data collection, may face increased risk of internal reconnaissance and potential data integrity issues. The impact is more pronounced in environments with poorly segmented internal networks or where internal services trust requests from the web server. While the vulnerability does not directly lead to data confidentiality loss or availability disruption, the indirect risks through chained attacks or internal service abuse could be significant. European entities in sectors such as finance, healthcare, and government, which often use WordPress for public-facing sites and have sensitive internal services, should be particularly vigilant. Additionally, compliance with GDPR mandates protection of personal data, and any internal service compromise could lead to regulatory consequences.

Immediate mitigation steps include disabling or uninstalling the vulnerable 'Block For Mailchimp – Easy Mailchimp Form Integration' plugin until a patch is available. If disabling is not feasible, restrict outbound HTTP/HTTPS requests from the web server hosting WordPress using firewall rules or egress filtering to prevent arbitrary external or internal requests initiated by the plugin. Implement strict network segmentation to limit the web server's ability to reach sensitive internal services. Monitor web server logs and network traffic for unusual outbound requests or patterns indicative of SSRF exploitation attempts. Employ Web Application Firewalls (WAFs) with custom rules to detect and block suspicious requests targeting the mcbSubmit_Form_Data() endpoint or exhibiting SSRF characteristics. Keep WordPress core and all plugins updated regularly and subscribe to vulnerability advisories for timely patching. Conduct internal audits of plugins and remove any unnecessary or unmaintained components. For cloud environments, restrict access to metadata services using instance metadata service (IMDS) version 2 or equivalent protections to mitigate SSRF abuse. Finally, educate development and operations teams about SSRF risks and secure coding practices to prevent similar vulnerabilities.