Vulnerability · Published Jun 5, 2026 · Assigned by GitHub_M

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

High 8.7

In plain English

A high-severity unrestricted file upload in haxcms-php from haxtheweb. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities).

Severity (CVSS 3.1)8.7High

Exploit odds (30 days)0.3%top 80.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
haxtheweb	haxcms-php	< 26.0.0

Weakness: CWE-178, CWE-434 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

References

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