CVE-2026-104021

What it 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.

At a glance

Exploitability

Can be exploited over the network with an admin-level account. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2026-10-01 17:00 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-10-10 05:16 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-10-13 13:30 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 7.2 HIGH (CVSS).
• Fix: none linked yet, which raises it.

Details

Published

2026-10-10 05:16 UTC

Last modified

2026-10-13 13:30 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-94 · Code injection

Record status

Deferred

Attack profile CVSS 3.1 · 7.2

Attack vector

Network

Complexity

Low

Privileges needed

High

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-104021.md and follow it. Check whether this project is affected by CVE-2026-104021. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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