CVE-2026-83627

What it is

The Hummingbird – Speed Optimization, Caching, Minify, Compress & CDN plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 3.21.0 via the log_msg() function in core/modules/class-page-cache.php. The page-cache debug log is written to wp-content/wphb-logs/page-caching-log.php, a directly web-accessible PHP file that is supposed to be protected by a leading '<?php die(); ?>' header. That header is guarded by class_exists( 'Filesystem' ), which can never match because class_exists() resolves string arguments in the global namespace while the class is Hummingbird\Core\Filesystem; when the log is created during a front-end request the header is therefore omitted entirely. get_cookies() then writes the raw name of any cookie matching the wphb_cache_ prefix into that file without sanitization. This makes it possible for unauthenticated attackers to write arbitrary PHP into the log file with a single anonymous request and execute it by requesting the file directly, resulting in full remote code execution. Exploitation requires the site administrator to have enabled Page Caching with the Debug Log option (non-default), and the log file to be created during a front-end request — a state reached by the plugin's own 'Clear logs' action, any cache flush, or unattended via the plugin's daily log-rotation cron, which can strip the protective header from an existing log file.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

1.4% 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. 2026-08-31 21:02 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-09-05 06:17 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-09-08 13:12 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.4% in the next 30 days (EPSS).
• Severity: 9.8 CRITICAL (CVSS).
• Fix: none linked yet, which raises it.

Details

Published

2026-09-05 06:17 UTC

Last modified

2026-09-08 13:12 UTC

Exploit probability

1.4% · EPSS, next 30 days

Weakness

CWE-94 · Code injection

Record status

Deferred

Attack profile CVSS 3.1 · 9.8

Attack vector

Network

Complexity

Low

Privileges needed

None

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-2026-83627.md and follow it. Check whether this project is affected by CVE-2026-83627. 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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