CVE-2024-2721: Sygnoos Social Media Share Buttons Flaw

CVE-2024-2721 Overview

CVE-2024-2721 is a PHP Object Injection vulnerability in the Sygnoos Social Media Share Buttons plugin for WordPress. The flaw stems from insecure deserialization of untrusted data [CWE-502] and affects all versions up to and including 2.1.0. An authenticated attacker with low privileges can submit crafted serialized input that the plugin unserializes, instantiating arbitrary PHP objects within the application context.

Critical Impact
Successful exploitation can lead to remote code execution, data tampering, or service disruption on affected WordPress sites when a suitable gadget chain is present.

Affected Products

Sygnoos Social Media Share Buttons for WordPress, versions up to and including 2.1.0
WordPress installations running the vulnerable plugin
Sites exposing plugin-handled endpoints to authenticated users

Discovery Timeline

2024-03-20 - CVE-2024-2721 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-2721

Vulnerability Analysis

The plugin passes attacker-controlled input to a PHP deserialization routine without validating or restricting the object types produced. When unserialize() processes a crafted payload, PHP invokes magic methods such as __wakeup(), __destruct(), or __toString() on the resulting objects. If the WordPress runtime or any loaded plugin exposes a usable gadget chain, this behavior escalates into arbitrary code execution or file operations.

The attack vector is network-based and requires low privileges but no user interaction. Because WordPress plugins share the same interpreter, a single deserialization sink can reach gadgets defined in core, themes, or unrelated plugins, expanding the practical impact well beyond the vulnerable component.

Root Cause

The root cause is unsafe use of PHP unserialize() on data influenced by an authenticated user. The plugin does not enforce an allowlist of classes with the allowed_classes option and performs no integrity check on the serialized blob before decoding it.

Attack Vector

An authenticated attacker submits a serialized PHP object to a plugin endpoint that processes settings or share data. The unserialization pipeline instantiates the object and triggers its magic methods, chaining into available gadgets to write files, execute commands, or manipulate site data. See the Patchstack Vulnerability Advisory for technical details.

// No verified public proof-of-concept is available for CVE-2024-2721.
// Refer to the Patchstack advisory linked above for technical context.

Detection Methods for CVE-2024-2721

Indicators of Compromise

HTTP POST requests to plugin endpoints containing serialized PHP markers such as O:, a:, or s: followed by class or property tokens
Unexpected PHP files, cron entries, or admin users created after requests reached the plugin
WordPress error log entries referencing unserialize(), __wakeup, or __destruct from plugin paths under wp-content/plugins/social-media-builder/

Detection Strategies

Inspect web server and WordPress logs for request bodies containing PHP serialization syntax targeting the Social Media Share Buttons plugin
Correlate authenticated low-privilege user sessions with subsequent file system changes under wp-content/
Monitor for outbound network connections initiated by the PHP worker process following requests to the plugin

Monitoring Recommendations

Enable WordPress audit logging for plugin option updates and settings changes
Alert on new or modified PHP files in wp-content/uploads/ and plugin directories
Track process creation from php-fpm or the web server user, which should not spawn shells under normal operation

How to Mitigate CVE-2024-2721

Immediate Actions Required

Update the Sygnoos Social Media Share Buttons plugin to a version later than 2.1.0 once the vendor publishes a fixed release
Restrict who can authenticate to WordPress by enforcing strong credentials and multi-factor authentication on all accounts
Review installed plugins and remove Social Media Share Buttons if a patched version is unavailable and the functionality is not essential

Patch Information

At the time of NVD publication the advisory indicated the issue affects versions up to and including 2.1.0. Consult the Patchstack Vulnerability Advisory and the plugin listing on WordPress.org for the current fixed version.

Workarounds

Deploy a web application firewall rule that blocks request bodies containing PHP serialization tokens directed at plugin endpoints
Deactivate the plugin until a patched release is installed and verified
Limit subscriber and contributor role assignments to reduce the pool of accounts able to reach the vulnerable endpoint

bash

# Temporarily deactivate the plugin using WP-CLI
wp plugin deactivate social-media-builder

# Update once a fixed version is released
wp plugin update social-media-builder