CVE-2025-34153 is a critical vulnerability affecting Hyland Software's OnBase product, specifically versions prior to 17.0.2.87, though other versions may also be impacted. The vulnerability arises from insecure deserialization of untrusted data within the .NET Remoting TCP channel. OnBase registers a listener on TCP port 6031 with the URI endpoint 'TimerServer', implemented in the Hyland.Core.Timers.dll assembly. This endpoint uses the .NET BinaryFormatter to deserialize incoming data without proper validation or sanitization, which is a known insecure practice. An attacker can exploit this flaw by sending specially crafted serialized objects to the TimerServer endpoint, leading to remote code execution (RCE) with NT AUTHORITY\SYSTEM privileges. This means the attacker gains full control over the affected system, enabling them to execute arbitrary commands, install malware, or move laterally within the network. The vulnerability requires no authentication or user interaction, making it highly exploitable remotely over the network. The CVSS 4.0 base score is 10.0, reflecting the maximum severity due to the combination of network attack vector, no required privileges or user interaction, and high impact on confidentiality, integrity, and availability. Although no known exploits are reported in the wild yet, the nature of the vulnerability and the widespread use of OnBase in enterprise environments make it a significant threat. The root cause is the use of BinaryFormatter, which is deprecated and unsafe for deserializing untrusted data, leading to CWE-502 (Deserialization of Untrusted Data). This vulnerability highlights the critical need for secure coding practices and timely patching in enterprise software.

For European organizations using Hyland OnBase, this vulnerability poses a severe risk. OnBase is widely used for enterprise content management, document management, and workflow automation across sectors such as healthcare, government, finance, and legal services. Exploitation could lead to full system compromise, data breaches involving sensitive personal and corporate data, disruption of critical business processes, and potential regulatory non-compliance under GDPR due to unauthorized access or data leakage. The ability to execute code as SYSTEM allows attackers to disable security controls, deploy ransomware, or establish persistent backdoors. Given the criticality and ease of exploitation, organizations face risks of operational downtime, reputational damage, and financial losses. The vulnerability also increases the attack surface for advanced persistent threats (APTs) targeting strategic European industries. The lack of authentication and user interaction requirements means that attackers can scan for exposed OnBase instances and exploit them remotely, potentially leading to widespread impact if not mitigated promptly.

1. Immediate application of vendor patches or updates once available is paramount; organizations should prioritize upgrading to OnBase version 17.0.2.87 or later. 2. Until patches are applied, restrict network access to TCP port 6031 using firewalls or network segmentation to limit exposure to trusted internal hosts only. 3. Monitor network traffic for unusual or unexpected connections to port 6031 and implement intrusion detection/prevention systems (IDS/IPS) signatures to detect exploitation attempts targeting the TimerServer endpoint. 4. Disable or remove the .NET Remoting TCP channel if it is not required for business operations, or configure OnBase to use more secure communication mechanisms. 5. Conduct thorough audits of OnBase deployments to identify exposed instances and verify that no unauthorized changes or backdoors exist. 6. Implement application whitelisting and endpoint protection solutions capable of detecting anomalous process execution resulting from exploitation. 7. Educate IT and security teams about the risks of insecure deserialization and the importance of secure coding practices to prevent similar vulnerabilities in custom integrations or other software components. 8. Maintain up-to-date asset inventories and vulnerability management processes to rapidly identify and remediate affected systems.