Atomicorp WAF Rule 300013

Rule Summary

• Rule ID: 300013
• Status: Active
• Alert message: Atomicorp.com WAF Rules - Virtual Just In Time Patch: SiYuan <= v3.5.9 - Cross Site Scripting CVE-2026-31809
• Observed CWEs: CWE-79 (5)
• Revision: 1
• Rule severity: Alert (1)
• Phase: 2 (request body)
• Request surfaces: Request URI
• Rule action: deny
• HTTP status: 403
• Logging: log, auditlog

Description

This rule detects behavior identified by its current alert as “Virtual Just In Time Patch: SiYuan <= v3.5.9 - Cross Site Scripting CVE-2026-31809” in the request URI. It evaluates during the request body phase and denies matching traffic with HTTP status 403.

CVEs Referenced by This Rule

The current ModSecurity rule metadata explicitly names the following CVEs. These references explain the rule author’s association; they do not claim that the rule is limited to these vulnerabilities or that this is an exhaustive coverage list.

CVE-2026-31809

SiYuan is a personal knowledge management system. Prior to 3.5.10, SiYuan’s SVG sanitizer (SanitizeSVG) checks href attributes for the javascript: prefix using strings.HasPrefix(). However, inserting ASCII tab (&#9;), newline (&#10;), or carriage return (&#13;) characters inside the javascript: string bypasses this prefix check. Browsers strip these characters per the WHATWG URL specification before parsing the URL scheme, so the JavaScript still executes. This allows an attacker to inject executable JavaScript into the unauthenticated /api/icon/getDynamicIcon endpoint, creating a reflected XSS. This is a second bypass of the fix for CVE-2026-29183 (fixed in v3.5.9). This vulnerability is fixed in 3.5.10.

• Association: The rule references CVE-2026-31809 in its alert message.
• CVE Record (opens in a new tab)
• NVD (opens in a new tab)

Selected Related CVEs

This is a selected list of documented research observations, not an exhaustive coverage matrix. Absence of a CVE does not imply absence of protection.

Observed CWEs

These CWEs are recorded on published CVEs in the selected observations associated with this rule. They are observational relationships, not a claim that the rule universally blocks every vulnerability assigned to a CWE.