CVE-2026-83627
Description
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
Propose a mitigation on Community Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
References
- https://plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L1973
- https://plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L1982
- https://plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L749
- https://plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L752
- https://plugins.trac.wordpress.org/changeset/3675836/hummingbird-performance/trunk/core/modules/class-page-cache.php
- https://plugins.trac.wordpress.org/changeset?old_path=%2Fhummingbird-performance/tags/3.20.0&new_path=%2Fhummingbird-performance/tags/3.21.2
- https://plugins.trac.wordpress.org/changeset?reponame=&new=3675836%40hummingbird-performance%2Ftags%2F3.21.2&old=3614991%40hummingbird-performance%2Ftags%2F3.20.0
- https://www.wordfence.com/threat-intel/vulnerabilities/id/65c3ca36-79e6-47f8-9524-27e7631f4caf?source=cve
CWEs
CWE-94
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.