CVE-2026-83627 json
Hummingbird – Speed Optimization, Caching, Minify, Compress & CDN <= 3.21.0 - Unauthenticated Remote Code Execution via Cookie Name in Page Cache Debug Log
published 2mo ago modified 2mo ago also EUVD-2026-71839
- cvss
- 9.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.4%
- EPSS 1.4% chance of exploitation in 30 days, percentile 73%
- public exploits
- 0
- none known
Summary
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.
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Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- total
- Assessed
- 2mo ago
Exploit prediction
1.43% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-11).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
Affected products
- wpmudev Hummingbird Performance – Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN
Classification
- Weakness
-
- CWE-94 Improper Control of Generation of Code
- Technology feeds
References
- wordfence.com /threat-intel/vulnerabilities/id/65c3ca36-79e6-47f8-9524-27e7631f4caf?source=cve
- plugins.trac.wordpress.org /browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L1982
- plugins.trac.wordpress.org /browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L1973
- plugins.trac.wordpress.org /browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L752
- plugins.trac.wordpress.org /browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L749
- plugins.trac.wordpress.org /changeset?reponame=&new=3675836%40hummingbird-performance%2Ftags%2F3.21.2&old=3614991%40hummingbird-performan
- plugins.trac.wordpress.org /changeset/3675836/hummingbird-performance/trunk/core/modules/class-page-cache.php
- plugins.trac.wordpress.org /changeset?old_path=%2Fhummingbird-performance/tags/3.20.0&new_path=%2Fhummingbird-performance/tags/3.21.2
Sources
- CVE List CVE-2026-83627
- NVD CVE-2026-83627
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.