CVE-2026-0773 in Upsonic
Summary
by MITRE • 01/23/2026
Upsonic Cloudpickle Deserialization of Untrusted Data Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of Upsonic. Authentication is not required to exploit this vulnerability.
The specific flaw exists within the add_tool endpoint, which listens on TCP port 7541 by default. The issue results from the lack of proper validation of user-supplied data, which can result in deserialization of untrusted data. An attacker can leverage this vulnerability to execute code in the context of the service account. Was ZDI-CAN-26845.
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Analysis
by VulDB Data Team • 01/25/2026
The CVE-2026-0773 vulnerability represents a critical remote code execution flaw in Upsonic Cloudpickle implementations that directly impacts the security posture of affected systems. This vulnerability resides within the add_tool endpoint that operates on TCP port 7541, making it accessible to remote attackers without requiring authentication credentials. The flaw stems from inadequate input validation mechanisms that permit deserialization of untrusted data, creating a pathway for malicious actors to inject and execute arbitrary code on target systems. The vulnerability's severity is amplified by its remote exploitability and the fact that it operates under the privileges of the service account, potentially allowing attackers to escalate their privileges and gain deeper system access.
The technical exploitation of this vulnerability follows the established patterns of deserialization attacks that have been documented in various security frameworks including CWE-502, which specifically addresses "Deserialization of Untrusted Data" as a critical weakness. Attackers can craft malicious payloads that, when processed by the vulnerable Cloudpickle deserialization mechanism, trigger unintended code execution. The attack surface is particularly concerning because the vulnerability exists in a network-accessible endpoint that does not require authentication, effectively removing any barrier to exploitation. This aligns with ATT&CK technique T1203, which covers "Exploitation for Client Execution" and demonstrates how unvalidated input can be leveraged to achieve remote code execution in service-oriented applications.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with the ability to operate within the security context of the service account. This privilege escalation potential means that successful exploitation could result in data exfiltration, system compromise, or further lateral movement within the network. Organizations relying on Upsonic Cloudpickle implementations face significant risk of unauthorized access and potential data breaches, especially in environments where the service operates with elevated privileges or has access to sensitive data repositories. The vulnerability's classification as a remote code execution flaw places it in the highest severity category according to industry standards, as it enables attackers to gain full control over affected systems without requiring physical access or valid credentials.
Mitigation strategies for CVE-2026-0773 should prioritize immediate patching of affected systems and implementation of network segmentation controls to restrict access to the vulnerable TCP port 7541. Organizations should deploy firewall rules to block external access to this port and implement proper input validation mechanisms that prevent deserialization of untrusted data. The solution architecture should incorporate principle of least privilege principles, ensuring that service accounts operate with minimal required permissions. Additionally, network monitoring should be enhanced to detect anomalous behavior patterns that might indicate exploitation attempts, while regular security assessments should verify that no unauthorized modifications have occurred. The remediation process must also include comprehensive vulnerability scanning to identify all instances of the vulnerable software across the organization's infrastructure, as the attack surface may extend beyond the primary service endpoint.