Docmost up to 0.23.x Mermaid Diagram mermaid.render cross site scripting

Summaryinfo

A vulnerability identified as problematic has been detected in Docmost up to 0.23.x. Affected is the function mermaid.render of the component Mermaid Diagram Handler. This manipulation causes cross site scripting. This vulnerability appears as CVE-2026-23630. The attack may be initiated remotely. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Docmost up to 0.23.x. Affected by this vulnerability is the function mermaid.render of the component Mermaid Diagram Handler. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

Docmost is open-source collaborative wiki and documentation software. In versions 0.3.0 through 0.23.2, Mermaid code block rendering is vulnerable to stored Cross-Site Scripting (XSS). The frontend can render attacker-controlled Mermaid diagrams using mermaid.render(), then inject the returned SVG/HTML into the DOM via dangerouslySetInnerHTML without sanitization. Mermaid per-diagram %%{init}%% directives allow overriding securityLevel and enabling htmlLabels, permitting arbitrary HTML/JS execution for any viewer. This issue has been fixed in version 0.24.0.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-23630 since 01/14/2026. The exploitation appears to be easy. The attack can be launched remotely. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

Upgrading to version 0.24.0 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch cb9f27da9a8b4940760e37e5238a1eb91e427daf is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• Docmost

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9
• 0.10
• 0.11
• 0.12
• 0.13
• 0.14
• 0.15
• 0.16
• 0.17
• 0.18
• 0.19
• 0.20
• 0.21
• 0.22
• 0.23

License

• open-source

Website

• Product: https://github.com/docmost/docmost/

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