CVE-2026-78277 in FluentCRM Pro Plugin
Summary
by MITRE • 08/24/2026
Subscriber Server Side Request Forgery (SSRF) in FluentCRM Pro <= 3.1.12 versions.
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Analysis
by VulDB Data Team • 08/24/2026
The vulnerability identified as Subscriber Server-Side Request Forgery, or SSRF, within FluentCRM Pro versions prior to 3.1.12 represents a critical security flaw that allows an attacker to manipulate the application into making HTTP requests to unintended destinations. This type of attack exploits the trust relationship between the web server and internal services by forcing the server to send a crafted request to a specific target domain or IP address, which is controlled by the user input rather than being strictly validated against a whitelist of allowed domains. In the context of FluentCRM Pro, this vulnerability specifically affects the subscriber management functionality, where user-supplied data is processed without adequate sanitization or validation before being used as part of an outbound network request initiated by the server itself.
From a technical perspective, the root cause lies in insufficient input validation and lack of URL scheme verification within the code handling subscriber-related operations. When a legitimate administrator or authorized user interacts with the plugin to manage subscribers, certain parameters may be passed directly into functions that perform HTTP requests, such as those used for verifying email addresses via pingbacks, fetching profile data from external services, or integrating with third-party APIs. If these inputs are not rigorously checked against a predefined allowlist of permitted hosts and protocols, an attacker can inject malicious URLs pointing to internal network resources, cloud metadata endpoints like AWS EC2 instance metadata service at 169.254.169.254, or local development servers running on localhost. This bypasses standard browser-based same-origin policies because the request originates from the server side, effectively allowing the attacker to probe and interact with internal infrastructure that is otherwise inaccessible from the public internet.
The operational impact of this vulnerability can be severe depending on the deployment environment and network architecture. In cloud-hosted environments, successful exploitation could lead to the exfiltration of sensitive instance metadata, including temporary security credentials, IAM role information, and other configuration details that provide further access vectors for deeper compromise. Within internal networks or private deployments, an attacker might use this SSRF vector to scan internal ports, interact with backend databases, admin panels, or microservices running on non-public interfaces, potentially leading to unauthorized data access, service disruption, or lateral movement within the network perimeter. Since FluentCRM Pro is often used by businesses for marketing and customer relationship management, a breach could result in significant reputational damage, loss of customer trust, and potential regulatory penalties under frameworks such as GDPR if personal subscriber data is exposed through these indirect channels.
This vulnerability aligns with CWE-918, which defines Server-Side Request Forgery (SSRF) flaws where the web server makes requests to a URL provided by an attacker without proper validation of the destination address or protocol. Furthermore, in terms of offensive security tactics, this behavior corresponds to ATT&CK technique T1571, specifically the component related to Non-Standard Ports and Services if internal services are accessed on unusual ports, or more broadly under reconnaissance activities where attackers gather information about network topology and available services. The lack of strict allowlisting for outbound connections is a common anti-pattern in web application development that leaves systems vulnerable to such manipulations even when traditional input validation measures appear robust against other attack vectors like SQL injection or cross-site scripting.
To mitigate this risk, immediate action should be taken by upgrading FluentCRM Pro to version 3.1.12 or later, where the developers have implemented proper safeguards including strict URL parsing and allowlisting mechanisms that restrict outbound requests to only known and trusted domains. For organizations unable to upgrade immediately due to compatibility constraints, implementing a web application firewall rule set can provide temporary protection by inspecting outgoing traffic from the server for suspicious patterns such as private IP ranges or cloud metadata endpoints. Additionally, developers should enforce strict input validation on all parameters involved in network operations, ensuring that only whitelisted domains and secure protocols like HTTPS are permitted. Network-level controls, including egress filtering at the firewall level to restrict outbound connections to necessary external services only, further reduce the attack surface by preventing the server from communicating with arbitrary internal or malicious destinations regardless of application-layer vulnerabilities.