critical CVSS 9.1

CVE-2021-4457·PHP vulnerability

The ZoomSounds plugin before 6.05 contains a PHP file allowing unauthenticated users to upload an arbitrary file anywhere on the web server.

Severity
critical
Software
PHP
Fixed in
6.05
Published
2025-06-25

Affected versions

Until: 6.05

Fixed in: 6.05

How to fix this CVE

If you are running the ZoomSounds plugin on a WordPress installation, upgrade immediately to version 6.05 or later. This plugin vulnerability allows attackers to upload malicious files to arbitrary locations on your web server without authentication. Review your web server's upload directories for suspicious files and monitor access logs for unauthorized file upload attempts.

sudo dnf update php

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST request to /wp-content/plugins/zoomsounds/ endpoints with multipart/form-data containing executable file extensions (.php, .php5, .phtml, .phar) without valid WordPress nonce or authentication headers

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Block unauthenticated POST requests to /wp-content/plugins/zoomsounds/ upload handlers; restrict file uploads in this directory to authenticated users only; implement file type validation to reject executable extensions (.php, .php5, .phtml, .phar, .exe) in upload directories

How to check if you are affected

  1. Step 1: Check installed PHP and ZoomSounds plugin version with: wp plugin list | grep -i zoomsounds
  2. Step 2: Verify if ZoomSounds is active and exposed by checking for the vulnerable upload handler file in your WordPress installation at /wp-content/plugins/zoomsounds/
  3. Step 3: Search web server logs for POST requests to upload endpoints without authentication: grep -i 'POST.*upload' /var/log/apache2/access.log | grep -v 'wp-admin'
  4. Step 4: Confirm the fix by running wp plugin list | grep -i zoomsounds and verifying the version is 6.05 or higher

FAQ

What is CVE-2021-4457?

This is a critical unauthenticated file upload vulnerability in the ZoomSounds WordPress plugin that allows remote attackers to upload arbitrary files anywhere on the web server's filesystem, potentially leading to remote code execution.

Is CVE-2021-4457 being actively exploited?

According to CISA's Known Exploited Vulnerabilities catalog, this CVE is not currently listed as actively exploited in the wild, but the severity and ease of exploitation make proactive patching essential.

What versions of the ZoomSounds plugin are affected by CVE-2021-4457?

All versions of ZoomSounds prior to 6.05 are vulnerable; version 6.05 and later contain the security fix.

How do I check if my server is vulnerable to CVE-2021-4457?

Run wp plugin list | grep -i zoomsounds to identify the installed version, or manually check /wp-content/plugins/zoomsounds/readme.txt for the version number. Any version below 6.05 is vulnerable.

Does Defensia detect CVE-2021-4457?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the ZoomSounds plugin is detected on a monitored WordPress installation, CVE-2021-4457 will appear in your dashboard with remediation steps.

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References

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