What’s Vulnerable › Vulnerabilities

CVE-2026-46392: HAX CMS PHP Has a Stored XSS via Case-Sensitivity Mismatch in HTML Upload Validation

• Severity: high (CVSS 8.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-05 · updated 2026-10-26
• Weakness: CWE-178

Description

HAX CMS helps manage microsite universe with PHP or NodeJs backends. Prior to version 26.0.0 of HAX CMS PHP, the `saveFile` endpoint validates upload extensions case-insensitively and writes the filename to disk verbatim, but the `.htaccess` rule that forces `Content-Disposition: attachment` on HTML files is case-sensitive. An HTML file uploaded with an uppercase extension (`.HTML`, `.Html`, `.HTM`) is still served as `text/html` but the forced-download header never applies, so the browser renders it inline and executes any embedded JavaScript in the HAXcms origin. This bypasses the mitigation shipped for CVE-2026-22704. Version 26.0.0 contains a fix.

Affected products

• haxtheweb haxcms-php: before 26.0.0

References

• https://github.com/haxtheweb/issues/security/advisories/GHSA-hg33-w4j2-95qp
• https://github.com/haxtheweb/issues/security/advisories/GHSA-hg33-w4j2-95qp

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