CVE-2026-104021
Received Received - Intake

Code Injection in Fastcache WordPress Plugin

Publication date: 2026-10-10

Last updated on: 2026-10-10

Assigner: Wordfence

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.

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Meta Information

Published
2026-10-10
Last Modified
2026-10-10
Generated
2026-10-10
AI Q&A
2026-10-10
EPSS Evaluated
N/A
NVD
CVE-2026-104021
EUVD
EUVD-2026-96068

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
hostspa Fastcache by Host.it 0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-94 The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.

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Executive Summary

This vulnerability is a code injection flaw in the Fastcache by Host.it WordPress plugin up to version 1.7.4. It occurs because the plugin does not properly sanitize user input in the cache_cookie_exclude parameter. Attackers with admin access can inject malicious Apache directives into the .htaccess file by exploiting improper handling of newline characters in input values.

Detection Guidance

Check WordPress sites using the Fastcache by Host.it plugin version 1.7.4 or lower. Inspect .htaccess files for unexpected Apache directives or PHP code injection. Look for unauthorized changes in server configuration files.

Impact Analysis

An attacker could exploit this to modify server configurations, such as adding malicious PHP code execution directives. This could lead to full server compromise, data theft, or unauthorized access to sensitive information. The impact requires admin-level access but enables severe server-side attacks.

Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality requirements. For HIPAA, it risks exposing protected health information. Compliance failures may result in legal penalties, fines, or reputational damage due to insufficient security controls.

Mitigation Strategies

Update the Fastcache plugin to the latest version. Remove the plugin if unused. Restrict admin-level access to trusted users only. Monitor .htaccess files for unauthorized modifications.

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