hostspa Fastcache by Host.it Plugin up to 1.7.4 on WordPress Cache Cookie Exclusion buildSiteHtaccessRules fastcache_settings[cache_cookie_exclude][] code injection

Summaryinfo

A vulnerability identified as problematic has been detected in hostspa Fastcache by Host.it Plugin up to 1.7.4. Impacted is the function buildSiteHtaccessRules of the component Cache Cookie Exclusion. This manipulation of the argument fastcache_settings[cache_cookie_exclude][] causes code injection. This vulnerability is tracked as CVE-2026-104021. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in hostspa Fastcache by Host.it Plugin up to 1.7.4 and classified as problematic. Affected by this vulnerability is the function buildSiteHtaccessRules of the component Cache Cookie Exclusion. The manipulation of the argument fastcache_settings[cache_cookie_exclude][] with an unknown input leads to a code injection vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at wordfence.com. This vulnerability is known as CVE-2026-104021 since 10/01/2026. The exploitation appears to be easy. The attack can be launched remotely. Additional levels of successful authentication are required for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/10/2026). The attack technique deployed by this issue is T1059 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-96068). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• WordPress Plugin

Vendor

• hostspa

Name

• Fastcache by Host.it Plugin

Version

• 1.7.0
• 1.7.1
• 1.7.2
• 1.7.3
• 1.7.4

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CPE 2.2info

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Be aware that VulDB is the high quality source for vulnerability data.

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