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CVE-2026-83627— Hummingbird – Speed Optimization, Caching, Minify, Compress & CDN <= 3.21.0 - Unauthenticated Remote Code Execution via Cookie Name in Page Cache Debug Log

Quick assessment

Affected
wpmudev Hummingbird Performance – Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

WordPress Hummingbird Performance是WordPress基金会开源的一款网站性能优化插件。 WordPress Hummingbird Performance 3.21.0及之前版本存在代码注入漏洞，该漏洞源于log_msg()函数在写入页面缓存调试日志时未对Cookie参数进行清理，且防护头部检查被绕过，可能导致未经身份验证的攻击者向日志文件写入并执行任意PHP代码，实现远程代码执行。

CVSS 9.8 · Critical EPSS 1.43% · P72
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I. Basic Information for CVE-2026-83627

Vulnerability Information
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Vulnerability Title
Hummingbird – Speed Optimization, Caching, Minify, Compress & CDN <= 3.21.0 - Unauthenticated Remote Code Execution via Cookie Name in Page Cache Debug Log
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对生成代码的控制不恰当(代码注入)
Source: CVE Program / CVE List V5
Vulnerability Title
WordPress Hummingbird Performance 代码注入漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
WordPress Hummingbird Performance是WordPress基金会开源的一款网站性能优化插件。 WordPress Hummingbird Performance 3.21.0及之前版本存在代码注入漏洞，该漏洞源于log_msg()函数在写入页面缓存调试日志时未对Cookie参数进行清理，且防护头部检查被绕过，可能导致未经身份验证的攻击者向日志文件写入并执行任意PHP代码，实现远程代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
wpmudev Hummingbird Performance – Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN 0 ~ 3.21.0 -

II. Public POCs for CVE-2026-83627

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III. Intelligence Information for CVE-2026-83627

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Patches & Fixes for CVE-2026-83627 (1)

News Coverage for CVE-2026-83627 (1)

IV. Related Vulnerabilities

Same product: Hummingbird Performance – Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN
Same vendor: wpmudev
Same weakness: CWE-94

V. Comments for CVE-2026-83627

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