CVE-2026-25992 is a path traversal vulnerability classified under CWE-22 that affects the SiYuan personal knowledge management system prior to version 3.5.5. The vulnerability exists in the /api/file/getFile endpoint, which attempts to prevent unauthorized file access by performing case-sensitive string equality checks on requested file paths. However, on case-insensitive file systems, notably Windows, this check can be bypassed by using mixed-case variations of the file path, allowing attackers to access files outside the intended restricted directories. This flaw enables unauthorized reading of sensitive configuration files without requiring authentication or user interaction, thereby compromising confidentiality. The vulnerability does not affect integrity or availability directly. The CVSS v3.1 base score is 7.5, reflecting network attack vector, low attack complexity, no privileges required, and no user interaction needed. Although no known exploits are reported in the wild, the vulnerability poses a significant risk due to its ease of exploitation and potential data exposure. The issue is resolved in SiYuan version 3.5.5 by correcting the pathname validation logic to properly handle case insensitivity on affected file systems.

For European organizations, this vulnerability can lead to unauthorized disclosure of sensitive configuration files, which may contain credentials, API keys, or other confidential information. This exposure can facilitate further attacks such as privilege escalation, lateral movement, or data breaches. Organizations using SiYuan on Windows-based environments are particularly vulnerable due to the case-insensitive file system behavior. The impact is heightened for sectors handling sensitive data, including finance, healthcare, and government entities. Confidentiality breaches can damage organizational reputation, lead to regulatory penalties under GDPR, and cause operational disruptions if attackers leverage exposed information. Although the vulnerability does not directly affect system integrity or availability, the indirect consequences of data exposure can be severe. The lack of required authentication and user interaction increases the risk of automated exploitation attempts.

The primary mitigation is to upgrade all SiYuan deployments to version 3.5.5 or later, where the vulnerability is fixed. Organizations should audit their current SiYuan versions and prioritize patching Windows-based systems. Until patching is complete, restrict access to the /api/file/getFile endpoint by implementing network-level controls such as IP whitelisting or VPN-only access. Employ web application firewalls (WAFs) to detect and block path traversal attempts, particularly those using mixed-case path variations. Conduct regular security assessments and code reviews for custom integrations with SiYuan to ensure no similar validation issues exist. Additionally, monitor logs for unusual file access patterns indicative of exploitation attempts. Educate developers and administrators about the risks of case sensitivity differences across file systems to prevent similar vulnerabilities in the future.