CVE-2025-39565 Overview
CVE-2025-39565 is a Deserialization of Untrusted Data vulnerability [CWE-502] in the Melapress MelaPress Login Security plugin for WordPress. The flaw enables PHP Object Injection in versions up to and including 2.1.0. An authenticated attacker with high privileges can submit crafted serialized payloads that the plugin deserializes without validation. Successful exploitation can lead to arbitrary code execution, data tampering, or service disruption on the affected WordPress site.
Critical Impact
Authenticated attackers can inject PHP objects to compromise confidentiality, integrity, and availability of the WordPress application running MelaPress Login Security <= 2.1.0.
Affected Products
- Melapress MelaPress Login Security (WordPress plugin)
- Versions from n/a through <= 2.1.0
- Free distribution channel on WordPress.org
Discovery Timeline
- 2025-04-16 - CVE-2025-39565 published to NVD
- 2026-04-23 - Last updated in NVD database
Technical Details for CVE-2025-39565
Vulnerability Analysis
The plugin processes serialized input through PHP's unserialize() function without validating the source or structure of the data. PHP Object Injection occurs when attacker-controlled serialized data is passed to deserialization routines. During object reconstruction, PHP triggers magic methods such as __wakeup(), __destruct(), and __toString() on the resulting objects.
If the WordPress environment exposes classes with exploitable magic methods, an attacker can chain them into a Property-Oriented Programming (POP) gadget. These gadgets can yield arbitrary code execution, file operations, or database changes within the scope of the PHP worker process.
The vulnerability requires high privileges, which limits the attacker pool to administrators or users with elevated roles inside the WordPress instance. However, exploitation does not require user interaction once the privileged session exists.
Root Cause
The root cause is unsafe deserialization of attacker-influenced input. The plugin does not enforce strict typing or use safer alternatives such as json_decode() for structured data. Any value reaching unserialize() is treated as authoritative, enabling object instantiation from arbitrary class definitions loaded by WordPress core, themes, or other active plugins.
Attack Vector
The attack vector is network-based. An authenticated administrator-level account submits a crafted payload to a plugin endpoint that handles serialized data. The plugin reconstructs the malicious object graph, triggering downstream gadget chains. The Patchstack advisory (Patchstack Vulnerability Report) documents the affected code paths and required preconditions.
No public proof-of-concept exploit is available at the time of publication, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog.
Detection Methods for CVE-2025-39565
Indicators of Compromise
- HTTP requests to MelaPress Login Security endpoints containing serialized PHP markers such as O:, a:, or s: in parameter values
- Unexpected PHP errors referencing unserialize(), __wakeup, or __destruct in WordPress logs
- New or modified administrator accounts, scheduled tasks, or wp_options entries following plugin requests
- Outbound connections from the PHP-FPM or web server process to unfamiliar hosts
Detection Strategies
- Inspect web server access logs for POST requests to plugin handlers containing serialized object signatures
- Monitor file integrity on wp-content/plugins/melapress-login-security/ and core WordPress directories
- Correlate administrator authentication events with subsequent plugin configuration changes
Monitoring Recommendations
- Enable verbose PHP error logging and forward logs to a central SIEM for pattern matching on deserialization signatures
- Alert on creation of PHP files within wp-content/uploads/ or other writable directories
- Track privileged WordPress role assignments and REST API calls from new IP addresses
How to Mitigate CVE-2025-39565
Immediate Actions Required
- Update MelaPress Login Security to a release later than 2.1.0 as soon as the vendor publishes a fixed version
- Audit all WordPress administrator accounts and remove unused or stale privileged users
- Rotate credentials and session tokens for any administrator account that may have been compromised
- Review the plugin's recent activity logs for unauthorized configuration changes
Patch Information
Refer to the Patchstack Vulnerability Report for the latest fixed version and vendor guidance. Apply the update through the WordPress admin dashboard or via wp-cli once available.
Workarounds
- Deactivate and remove the MelaPress Login Security plugin until a patched release is installed
- Restrict administrator access using IP allowlists at the web server or WAF layer
- Enforce multi-factor authentication on all privileged WordPress accounts to reduce the risk of credential abuse
- Deploy a WAF rule to block requests containing serialized PHP object patterns targeting the plugin's endpoints
# Update the plugin via wp-cli once a fixed version is released
wp plugin update melapress-login-security
# Or deactivate and remove the plugin as a temporary workaround
wp plugin deactivate melapress-login-security
wp plugin uninstall melapress-login-security
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
