CVE-2025-68948 identifies a security weakness in the SiYuan Note application, a self-hosted, open-source personal knowledge management tool. In versions 3.5.1 and prior, the application uses a hardcoded cryptographic secret to encrypt session data, specifically the session store containing the AccessAuthCode. This practice violates secure cryptographic principles (CWE-321), as hardcoded keys are easily discoverable and cannot be rotated or individualized per user or installation. The AccessAuthCode is stored within the session cookie in encrypted form; however, due to the hardcoded key, an attacker who intercepts or otherwise obtains the encrypted cookie can decrypt it locally without needing network access or elevated privileges. Once decrypted, the attacker gains access to the AccessAuthCode in plaintext, which can be used to authenticate as the user or hijack their session, effectively bypassing authentication controls. The vulnerability requires no user interaction and can be exploited remotely with network access to the session cookie, such as through session hijacking techniques. The CVSS 4.0 score of 6.9 reflects a medium severity, considering the network attack vector, no required privileges or user interaction, and limited impact confined to confidentiality and integrity of session data. No patches or exploit code are currently publicly available, but the vulnerability poses a significant risk to user account security and data confidentiality within affected deployments.

For European organizations, this vulnerability threatens the confidentiality and integrity of user sessions within SiYuan Note deployments. Attackers who successfully exploit this flaw can impersonate legitimate users, gaining unauthorized access to sensitive personal knowledge data, potentially leading to data breaches or further lateral movement within an organization’s network. Since SiYuan Note is self-hosted, organizations with less mature security practices or inadequate network protections are at higher risk. The exposure of AccessAuthCode could also facilitate persistent unauthorized access if session tokens are long-lived or not properly invalidated. While availability is not directly impacted, the compromise of user sessions undermines trust and could lead to reputational damage. Organizations relying on SiYuan Note for critical knowledge management should consider this vulnerability a significant risk, especially in sectors handling sensitive or regulated information such as finance, healthcare, or government. The lack of known exploits in the wild provides a window for proactive mitigation before active attacks emerge.

To mitigate CVE-2025-68948, organizations should upgrade SiYuan Note to a version beyond 3.5.1 once a patch is released that removes the hardcoded cryptographic key and implements secure key management practices, such as per-installation unique keys or integration with secure key vaults. Until an official patch is available, organizations should restrict network access to the SiYuan Note instance and enforce strict transport layer security (TLS) to prevent session cookie interception. Implementing HTTP-only and Secure flags on cookies can reduce exposure to client-side attacks. Regularly rotating session secrets and invalidating existing sessions can limit the window of exploitation. Monitoring for unusual session activity or multiple concurrent sessions from different IPs may help detect hijacking attempts. Educating users about the risks of session hijacking and encouraging the use of VPNs or secure networks when accessing SiYuan Note can further reduce risk. Finally, organizations should consider isolating SiYuan Note instances within segmented network zones to limit lateral movement if compromise occurs.