CVE-2025-56223 identifies a denial of service vulnerability in the document upload component (/Home/UploadStreamDocument) of SigningHub version 8.6.8. The root cause is the absence of rate limiting controls on the upload functionality, which allows an attacker to send a large volume of file upload requests in rapid succession. This can exhaust server resources such as CPU, memory, or storage, leading to degraded performance or complete service outage. The vulnerability does not require authentication or user interaction, making it accessible to unauthenticated remote attackers. SigningHub is a digital signature and document workflow platform used by enterprises to manage electronic signatures and document approvals. The lack of rate limiting is a common oversight that can be exploited to disrupt service availability, impacting business continuity. No CVSS score has been assigned yet, and no public exploits have been observed. However, the vulnerability’s characteristics suggest it could be weaponized for denial of service attacks, especially in environments with high document upload activity.

For European organizations, the primary impact is service unavailability or degradation of SigningHub platforms, which can interrupt critical document signing and approval workflows. This disruption could delay business operations, affect compliance with legal or regulatory requirements for document handling, and damage organizational reputation. Sectors such as finance, legal, government, and healthcare that rely heavily on secure and timely document processing are particularly vulnerable. Additionally, denial of service incidents can lead to increased operational costs due to incident response and recovery efforts. The lack of authentication requirement broadens the attack surface, allowing external threat actors to target organizations indiscriminately. Given the increasing reliance on digital signature platforms in Europe, this vulnerability could have widespread operational consequences if exploited.

Organizations should implement strict rate limiting controls on the /Home/UploadStreamDocument endpoint to restrict the number of upload requests per user or IP address within a defined time window. Deploying web application firewalls (WAFs) with custom rules to detect and block abnormal upload patterns can provide an additional layer of defense. Monitoring upload traffic for spikes or unusual activity is critical to early detection of exploitation attempts. Applying patches or updates from the vendor once available is essential. In the absence of vendor patches, organizations can consider temporary mitigations such as disabling or restricting the upload functionality to trusted users only. Network-level protections like IP reputation filtering and geo-blocking may reduce exposure to external attackers. Finally, conducting regular security assessments and penetration testing on document management systems can help identify similar weaknesses proactively.