dbcve.org
Unrestricted File UploadWeakness · CWE-434

CVE-2026-15158

CRITICAL · 9.8 CVSS v3.1 Published 2026-07-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 6 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The Blocksy Companion plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 2.1.46 via the save_attachments function. This is due to the Custom Fonts extension registering a wp_check_filetype_and_ext filter that approves any filename containing .woff2 or .ttf as a substring via strpos() rather than validating that those strings appear as the final extension via PATHINFO_EXTENSION — allowing double-extension filenames such as shell.woff2.php to pass MIME validation and be handled as permitted font files. This makes it possible for unauthenticated attackers to upload files that may be executable, which makes remote code execution possible. This vulnerability is only exploitable when the premium version of the plugin (blocksy-companion-pro) is installed with both the WooCommerce Extra (Advanced Reviews) and Custom Fonts extensions active; the free blocksy-companion plugin does not contain the vulnerable code paths.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The Blocksy Companion premium plugin (blocksy-companion-pro) contains an arbitrary file upload vulnerability in the Custom Fonts extension's save_attachments function. The wp_check_filetype_and_ext filter uses strpos() to check if '.woff2' or '.ttf' appears anywhere in the filename rather than validating the actual file extension, allowing malicious double extensions like shell.woff2.php to bypass MIME validation and achieve remote code execution.

MitigationDisable the Custom Fonts and WooCommerce Extra (Advanced Reviews) extensions immediately if the premium version (2.1.46 or earlier) is in use, or apply an official patch once available. Implement web application firewall rules to block file uploads with double extensions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify Blocksy Companion premium plugin is installed
    Navigate to WordPress admin > Plugins and confirm blocksy-companion-pro is listed as an active plugin
    Affected if The plugin blocksy-companion-pro is installed and active
  2. Check installed plugin version
    In WordPress admin > Plugins, click on the blocksy-companion-pro plugin to view its version information, or check the plugin header in wp-content/plugins/blocksy-companion-premium/blocksy-companion.php
    Affected if The installed version is 2.1.46 or earlier
  3. Confirm if Custom Fonts extension is enabled
    Navigate to Blocksy > Extensions and verify if the Custom Fonts extension is active, or check for the presence of the custom-fonts directory in wp-content/plugins/blocksy-companion-premium/extensions/
    Affected if The Custom Fonts extension is enabled and active
  4. Inspect uploads directory for suspicious files
    Check wp-content/uploads/ and its subdirectories for files with double extensions such as *.woff2.php, *.ttf.php, or other anomalous file combinations
    Affected if Any uploaded files with double extensions containing .woff2 or .ttf followed by another extension are present

You are affected if blocksy-companion-pro version 2.1.46 or earlier is installed with the Custom Fonts extension enabled, or if suspicious double-extension files exist in your uploads directory.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Disable the Custom Fonts and WooCommerce Extra (Advanced Reviews) extensions immediately if the premium version (2.1.46 or earlier) is in use, or apply an official patch once available. Implement web application firewall rules to block file uploads with double extensions.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,750
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-15158 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data