CVE-2026-23645 is a medium-severity Stored Cross-Site Scripting (XSS) vulnerability in the b3log SiYuan software. This vulnerability allows attackers to execute arbitrary JavaScript code by uploading malicious SVG files. The vulnerability exists in SiYuan Note prior to version 3.5.4-dev2, and it is due to the application failing to sanitize uploaded SVG files. If a user uploads such a file, it can lead to code execution in the context of their authenticated session.
The CVSS score for this vulnerability is 5.3, indicating a medium severity level. The attack vector is network-based, requiring low complexity to exploit, and no privileges are required. However, user interaction is necessary, as users must actively upload the malicious SVG file.
Organizations should prioritize patching immediately to mitigate risks associated with this vulnerability. The vulnerability has been fixed in version 3.5.4-dev2 of SiYuan.
Given the nature of this vulnerability, it poses a risk to organizations that use SiYuan for personal knowledge management. The ease of exploitation combined with the potential for arbitrary code execution makes it critical for users to update to the latest version.
Vulnerability Details
The vulnerability description states: SiYuan is self-hosted, open source personal knowledge management software. Prior to 3.5.4-dev2, a Stored Cross-Site Scripting (XSS) vulnerability exists in SiYuan Note. The application does not sanitize uploaded SVG files. If a user uploads and views a malicious SVG file (e.g., imported from an untrusted source), arbitrary JavaScript code is executed in the context of their authenticated session. This vulnerability is fixed in 3.5.4-dev2.
The CVSS score of 5.3 signifies a medium severity, as it poses a moderate risk that could potentially be exploited by attackers. The vulnerability is classified under CWE-79, indicating it is related to improper neutralization of input during web page generation (XSS).
Technical Analysis
The root cause of this vulnerability lies in the failure of the application to sanitize SVG files upon upload. Attackers may leverage this vulnerability by uploading specially crafted SVG files that contain malicious JavaScript code. The attack vector is network-based, as the malicious SVG file can be uploaded via the application interface. The attack complexity is low, requiring no special skills or tools beyond basic knowledge of web application functionality.
No special privileges are required to exploit this vulnerability, making it accessible to a broad range of attackers. User interaction is necessary, as the victim must upload and view the malicious SVG file. The impact on confidentiality and integrity is low, as it does not directly compromise sensitive data but may allow unauthorized actions within the authenticated session.
Risk & Impact Analysis
Risk to organizations includes potential unauthorized actions performed in the context of an authenticated user, leading to data manipulation or exposure. The blast radius could be significant if an attacker successfully executes JavaScript on the client-side, potentially leading to further exploits. Organizations should assess the impact of this vulnerability, especially if they utilize SiYuan for storing sensitive information.
According to the Exploit Prediction Scoring System (EPSS), the score of 0.00016 indicates a very low likelihood of exploitation in the wild, which may provide some reprieve. However, the lack of a known exploit does not diminish the necessity for immediate action. Organizations should address this vulnerability by updating to the patched version, prioritizing it in their patch management cycle.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects all versions of SiYuan prior to version 3.5.4-dev2. Specifically, it is present in version 3.5.4:dev1 and earlier versions, which do not sanitize uploaded SVG files.
Mitigation & Remediation
Organizations should update to version 3.5.4-dev2 or later to remediate this vulnerability. For environments where immediate patching is not feasible, it is recommended to implement file upload restrictions to sanitize or validate SVG files before processing them. Regularly updating and reviewing application security configurations can help mitigate such vulnerabilities.
For further guidance, organizations may refer to our application security assessment services.
Detection Guidance
Monitoring for unusual file uploads or access patterns can help detect potential exploitation of this vulnerability. Log analysis should focus on user-uploaded files, especially SVG files, and any execution of JavaScript in user sessions should be closely examined for anomalies.
AppSecure Threat Intelligence Insight
The long-term significance of this vulnerability lies in its demonstration of the risks associated with file upload functionalities in web applications. Security teams should take this incident as a reminder to implement robust validation and sanitization mechanisms for all user-generated content.
Patterns of similar vulnerabilities may emerge, highlighting the need for continuous security training and awareness within development teams. Organizations can benefit from adopting a proactive security posture, integrating security into the software development lifecycle.
For further insights, we recommend reviewing our blog on penetration testing methodology and how it can enhance your security posture.
Additionally, our article on vulnerability management program design offers insights into creating a structured approach to manage such risks.
Finally, organizations should consider our API penetration testing guide to further enhance their security measures.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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