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CVE-2026-83627 (GCVE-0-2026-83627)

Vulnerability from cvelistv5 – Published: 2026-09-05 05:30 – Updated: 2026-09-05 05:30
VLAI
Title
Hummingbird – Speed Optimization, Caching, Minify, Compress & CDN <= 3.21.0 - Unauthenticated Remote Code Execution via Cookie Name in Page Cache Debug Log
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.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
  • CWE-94 - Improper Control of Generation of Code ('Code Injection')
Assigner
References
Impacted products
Credits
Kuba
Show details on NVD website
To clipboard 

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        {
          "defaultStatus": "unaffected",
          "product": "Hummingbird Performance \u2013 Cache \u0026 Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN",
          "vendor": "wpmudev",
          "versions": [
            {
              "lessThanOrEqual": "3.21.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Kuba"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "The Hummingbird \u2013 Speed Optimization, Caching, Minify, Compress \u0026 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 \u0027\u003c?php die(); ?\u003e\u0027 header. That header is guarded by class_exists( \u0027Filesystem\u0027 ), 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 \u2014 a state reached by the plugin\u0027s own \u0027Clear logs\u0027 action, any cache flush, or unattended via the plugin\u0027s daily log-rotation cron, which can strip the protective header from an existing log file."
        }
      ],
      "metrics": [
        {
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            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
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      "problemTypes": [
        {
          "descriptions": [
            {
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              "description": "CWE-94 Improper Control of Generation of Code (\u0027Code Injection\u0027)",
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        "shortName": "Wordfence"
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        },
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          "url": "https://plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L1982"
        },
        {
          "url": "https://plugins.trac.wordpress.org/browser/hummingbird-performance/trunk/core/modules/class-page-cache.php#L1973"
        },
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        },
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        },
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        },
        {
          "url": "https://plugins.trac.wordpress.org/changeset/3675836/hummingbird-performance/trunk/core/modules/class-page-cache.php"
        },
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      ],
      "timeline": [
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          "lang": "en",
          "time": "2026-08-31T21:21:47.000Z",
          "value": "Vendor Notified"
        },
        {
          "lang": "en",
          "time": "2026-09-04T17:05:27.000Z",
          "value": "Disclosed"
        }
      ],
      "title": "Hummingbird \u2013 Speed Optimization, Caching, Minify, Compress \u0026 CDN \u003c= 3.21.0 - Unauthenticated Remote Code Execution via Cookie Name in Page Cache Debug Log"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "b15e7b5b-3da4-40ae-a43c-f7aa60e62599",
    "assignerShortName": "Wordfence",
    "cveId": "CVE-2026-83627",
    "datePublished": "2026-09-05T05:30:54.821Z",
    "dateReserved": "2026-08-31T21:02:35.689Z",
    "dateUpdated": "2026-09-05T05:30:54.821Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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      "date": "2026-09-05",
      "epss": "0.00824",
      "percentile": "0.54589"
    },
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  }
}



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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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