CVE-2025-58218: USPS Edition Object Injection Vulnerability

CVE-2025-58218 Overview

CVE-2025-58218 is a PHP Object Injection vulnerability affecting the Eniture Technology Small Package Quotes – USPS Edition WordPress plugin. The flaw stems from deserialization of untrusted data [CWE-502] and impacts all versions up to and including 1.3.9. An authenticated attacker with high privileges can supply crafted serialized input that the plugin deserializes, enabling object injection against the host application. Successful exploitation can lead to code execution, data tampering, or denial of service depending on available gadget chains in the WordPress runtime.

Critical Impact

Authenticated object injection in the Small Package Quotes – USPS Edition plugin can compromise WordPress site confidentiality, integrity, and availability.

Affected Products

• Eniture Technology Small Package Quotes – USPS Edition WordPress plugin
• All versions from n/a through <= 1.3.9
• WordPress sites with the small-package-quotes-usps-edition plugin installed

Discovery Timeline

• 2025-08-27 - CVE-2025-58218 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-58218

Vulnerability Analysis

The vulnerability is classified under [CWE-502]: Deserialization of Untrusted Data. The plugin passes attacker-controlled input to a PHP deserialization routine without validating or restricting the object types that can be instantiated. When PHP unserializes attacker-supplied data, magic methods such as __wakeup, __destruct, or __toString execute on the resulting objects. Attackers can chain these methods with classes already loaded by WordPress core, themes, or other plugins to achieve secondary impacts including arbitrary file read, file write, or remote code execution.

The attack requires network access and high privileges on the target site but does not require user interaction. Because the impact extends across confidentiality, integrity, and availability, a successful chain typically results in full site compromise.

Root Cause

The root cause is unsafe use of unserialize() (or an equivalent deserialization function) on data sourced from a request or stored input controlled by an authenticated user. The plugin does not enforce an allowlist of expected classes via the allowed_classes option and does not validate input structure before deserialization.

Attack Vector

An authenticated attacker with high privileges submits a crafted serialized payload to a plugin endpoint that processes USPS shipping quote parameters. The plugin deserializes the payload, instantiating PHP objects whose magic methods trigger a gadget chain. The attack is delivered over the network without user interaction.

No public proof-of-concept code is available. Refer to the Patchstack Vulnerability Report for additional technical details.

Detection Methods for CVE-2025-58218

Indicators of Compromise

• HTTP requests to plugin endpoints containing serialized PHP markers such as O:, a:, or s: followed by class names and lengths.
• Unexpected PHP errors referencing __wakeup, __destruct, or undefined classes in PHP error logs.
• Creation or modification of PHP files under wp-content/uploads/ or plugin directories following plugin requests.
• New administrator accounts or unauthorized changes to wp_options entries after plugin interaction.

Detection Strategies

• Inspect web server access logs for POST requests to small-package-quotes-usps-edition plugin paths containing serialized object patterns.
• Monitor WordPress audit logs for privileged user activity correlated with plugin endpoints.
• Apply WAF rules that flag serialized PHP payloads in request bodies and query strings.

Monitoring Recommendations

• Forward WordPress application logs, PHP-FPM error logs, and web server logs to a centralized logging platform for correlation.
• Alert on file integrity changes in WordPress plugin and upload directories.
• Track privileged account behavior and flag unusual session activity targeting plugin administration pages.

How to Mitigate CVE-2025-58218

Immediate Actions Required

• Inventory all WordPress sites and identify installations of the small-package-quotes-usps-edition plugin at version 1.3.9 or earlier.
• Deactivate the plugin on affected sites until a patched version is verified and deployed.
• Rotate credentials for privileged WordPress accounts and review administrator account membership.
• Audit plugin-related endpoints in WAF logs for prior exploitation attempts.

Patch Information

At the time of NVD publication, the advisory indicates the vulnerability affects versions through 1.3.9 with no fixed version listed. Monitor the Patchstack Vulnerability Report and the vendor's plugin page for an updated release, and apply it as soon as it becomes available.

Workarounds

• Remove or deactivate the plugin on production sites until a vendor patch is published.
• Restrict access to WordPress administration paths using IP allowlists or VPN gating to reduce the high-privileged attack surface.
• Deploy WAF signatures that block requests containing PHP serialized object markers targeting plugin endpoints.
• Apply the principle of least privilege to all WordPress user accounts to limit who can reach the vulnerable code path.

# Configuration example: disable the vulnerable plugin via WP-CLI
wp plugin deactivate small-package-quotes-usps-edition
wp plugin status small-package-quotes-usps-edition