Hummingbird – Speed Optimization, Caching, Minify, Compress & CDN <= 3.21.0 - Unauthenticated Remote Code Execution via Cookie Name in Page Cache Debug Log

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-83627
StatePUBLISHED
AssignerWordfence
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-05 06:17:10 UTC
Updated2026-09-05 06:17:10 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-94 | CWE-94 CWE-94 Improper Control of Generation of Code ('Code Injection')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Wpmudev Hummingbird Performance Cache Page Speed Optimization For Core Web Vitals Critical CSS Minify CSS Defer CSS Javascript CDN affected 3.21.0 semver Not specified

References

ReferenceSourceLinkTags
plugins.trac.wordpress.org/changeset [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/changeset [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/changeset/3675836/hummingbird-performance/trunk/core/modules/... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page... [email protected] plugins.trac.wordpress.org
www.wordfence.com/threat-intel/vulnerabilities/id/65c3ca36-79e6-47f8-9524-27e76... [email protected] www.wordfence.com
plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page... [email protected] plugins.trac.wordpress.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Kuba (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-08-31T21:21:47.000ZVendor Notified
CNA2026-09-04T17:05:27.000ZDisclosed

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