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Modern Events Calendar LiteWordPress extension · Webnus

CVE-2021-4458

CRITICAL · 9.8 CVSS v3.1 Published 2025-07-12
Fix available
A fix is available. Upgrade to 6.4.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

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 Modern Events Calendar Lite plugin for WordPress is vulnerable to SQL Injection via the 'id' parameter of the 'wp_ajax_mec_load_single_page' AJAX action in all versions up to, and including, 6.3.0 due to insufficient escaping on the user supplied parameter and lack of sufficient preparation on the existing SQL query. This makes it possible for unauthenticated attackers to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database. This is only exploitable on sites with addslashes disabled.

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

SQL Injection vulnerability in Modern Events Calendar Lite WordPress plugin (versions up to 6.3.0) via the 'id' parameter in the wp_ajax_mec_load_single_page AJAX action. Insufficient input escaping and lack of prepared statements allow unauthenticated attackers to inject arbitrary SQL queries, but only when addslashes is disabled.

MitigationUpdate Modern Events Calendar Lite plugin to version 6.3.1 or later. If immediate updating is not feasible, disable the affected AJAX endpoint or ensure addslashes is enabled as a temporary workaround.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Modern Events Calendar LiteWordPress extension
Affected:< 6.4.0

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. Identify if Modern Events Calendar Lite plugin is installed
    Check the WordPress plugins directory or access the Plugins admin page to list installed plugins and locate 'Modern Events Calendar Lite' or 'MEC Lite'
    Affected if Plugin is not found or not installed, then not affected
  2. Determine the installed plugin version
    View the plugin details in WordPress admin (Plugins > Installed Plugins > Modern Events Calendar Lite > View Details) or inspect the main plugin file header for the Version field
    Affected if Version is 6.3.0 or lower (anything less than 6.4.0)
  3. Verify the AJAX endpoint is accessible
    Test access to /wp-admin/admin-ajax.php?action=mec_load_single_page or verify the action is registered in plugin code (look for add_action('wp_ajax_mec_load_single_page', ...) and add_action('wp_ajax_nopriv_mec_load_single_page', ...))
    Affected if AJAX action is registered and publicly accessible (wp_ajax_nopriv_ hook exists)
  4. Check PHP configuration for addslashes protection status
    Review PHP configuration (php.ini, .htaccess, or wp-config.php) for any settings that disable addslashes, or create a PHP info page to check if addslashes is explicitly disabled
    Affected if addslashes function is disabled or circumvented in the PHP environment

Environment is affected if Modern Events Calendar Lite version is below 6.4.0, the mec_load_single_page AJAX endpoint is accessible to unauthenticated users, AND addslashes is disabled in the PHP configuration.

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.

dbcve · scoped
Upgrade available Upgrade to 6.4.0 or later
Fixed in 6.4.0
Vendor patch plugins.trac.wordpress.org →
Interim mitigation

Update Modern Events Calendar Lite plugin to version 6.3.1 or later. If immediate updating is not feasible, disable the affected AJAX endpoint or ensure addslashes is enabled as a temporary workaround.

Recommended fix High confidence

Modern Events Calendar Lite version 6.4.0

  1. Backup your WordPress site and database before making any changes
  2. Update Modern Events Calendar Lite plugin to version 6.4.0 or later via the WordPress admin dashboard (Plugins > Add New > Upload or directly from the WordPress plugin repository)
  3. Alternatively, update via FTP/SFTP by uploading the new version files from https://wordpress.org/plugins/modern-events-calendar-lite/
  4. After updating, verify the version number reflects 6.4.0 or higher in Plugins > Installed Plugins
  5. Test the MEC functionality (create/view events) to ensure the plugin works correctly post-update
  6. Clear any caching plugins or server-side caches to ensure the patched code is served

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Modern Events Calendar Lite Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,696.

Scan for this in your stack

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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-2021-4458 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