CVE-2026-82233 in SiYuan
Summary
by MITRE • 08/28/2026
SiYuan before v3.8.1 contains a path traversal vulnerability in the asset.upload MCP tool that accepts arbitrary absolute file paths without workspace boundary validation. Attackers can induce the AI Agent to upload sensitive files such as SSH keys or credentials from outside the workspace into the asset directory through prompt injection.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 08/28/2026
The identified security flaw resides within the SiYuan application, specifically affecting versions prior to 3.8.1, and centers on a critical path traversal vulnerability embedded in the asset.upload MCP tool. This component is designed to handle file uploads but fails to implement adequate validation mechanisms for absolute file paths provided by external inputs. The core technical deficiency lies in the absence of workspace boundary enforcement, which allows an attacker to bypass intended directory restrictions. By supplying arbitrary absolute file system paths rather than relative or sanitized path structures, the vulnerability enables direct access to locations outside the designated secure workspace environment. This lack of input validation represents a fundamental failure in enforcing least privilege and containment principles within the application's architecture.
The operational impact of this vulnerability is significant due to its interaction with AI Agent capabilities through prompt injection techniques. An adversary can craft malicious prompts that exploit the natural language processing interface to trick the AI agent into executing file upload operations targeting sensitive system resources. Because the tool accepts absolute paths without verification, attackers can specify locations containing critical security artifacts such as SSH private keys, database credentials, or other authentication tokens stored on the host machine. The successful exploitation of this flaw results in the unauthorized exfiltration of these high-value assets to a location controlled by the attacker within the asset directory structure. This process effectively bypasses traditional perimeter defenses and user access controls that rely on workspace isolation for security assurance.
From an industry standards perspective, this vulnerability aligns with CWE-22 Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal or directory traversal. The failure to restrict file operations to the intended working directory allows unauthorized reading and writing capabilities across the broader file system. Furthermore, the exploitation method involving prompt injection to manipulate an AI agent correlates with MITRE ATT&CK techniques related to Command and Control via Application Layer Protocol, specifically leveraging LLM-driven automation for data exfiltration. The scenario also reflects aspects of CWE-78 Improper Neutralization of Special Elements used in an OS Command where user input is not properly sanitized before being processed by system-level functions that interpret file paths.
Mitigation strategies must prioritize immediate patching to version 3.8.1 or later, which addresses the underlying validation logic within the asset.upload MCP tool. In addition to software updates, defensive configurations should enforce strict allow-listing of permitted directories for any upload operations performed by AI agents. Input sanitization routines must be implemented to reject absolute paths and ensure all file references remain strictly within the predefined workspace boundaries. Security teams should also monitor logs for unusual patterns in prompt inputs that attempt to reference system-level directories or sensitive configuration files, as these serve as indicators of attempted exploitation against this specific vulnerability vector.