CVE-2026-62107: Masteriyo LMS Object Injection Vulnerability

CVE-2026-62107 Overview

CVE-2026-62107 is a PHP Object Injection vulnerability affecting the Masteriyo Learning Management System (LMS) plugin for WordPress in versions 3.4.0 and earlier. The flaw is classified under [CWE-502] Deserialization of Untrusted Data. An attacker with low privileges can supply crafted serialized input that the plugin deserializes, triggering unsafe object instantiation within the PHP runtime. When combined with a suitable POP (Property-Oriented Programming) chain from the WordPress core or other installed plugins, the issue can lead to remote code execution, data tampering, or full site compromise. The vulnerability was disclosed through Patchstack's coordinated disclosure program.

Critical Impact
Attackers can leverage insecure deserialization to execute arbitrary PHP objects, potentially achieving remote code execution and full WordPress site compromise.

Affected Products

Masteriyo LMS WordPress plugin versions 3.4.0 and earlier
WordPress sites running the learning-management-system plugin
Any environment exposing the vulnerable Masteriyo endpoints to authenticated low-privilege users

Discovery Timeline

2026-09-11 - CVE-2026-62107 published to the National Vulnerability Database (NVD)
2026-09-11 - Last updated in NVD database

Technical Details for CVE-2026-62107

Vulnerability Analysis

The vulnerability stems from the Masteriyo LMS plugin passing attacker-controlled input to a PHP deserialization function such as unserialize() without adequate validation. When PHP deserializes a crafted string, it reconstructs objects and invokes magic methods including __wakeup(), __destruct(), and __toString(). These automatic method calls create opportunities to chain gadgets from loaded classes across the WordPress runtime.

Because WordPress installations typically load many plugins and libraries, the pool of exploitable POP chains is large. An attacker who identifies a usable gadget chain can escalate the injection into arbitrary file writes, SQL execution, or remote code execution. The vulnerability is exploitable over the network with low attack complexity.

Root Cause

The root cause is the unsafe handling of serialized PHP data on an input path reachable by an authenticated user. Masteriyo processes serialized payloads without enforcing type restrictions, cryptographic integrity checks, or allow-lists of expected classes. This behavior corresponds to [CWE-502] Deserialization of Untrusted Data.

Attack Vector

Exploitation requires network access and low-level authentication to the target WordPress site. The attacker submits a serialized PHP object to a vulnerable Masteriyo endpoint. Successful exploitation yields high impact to confidentiality, integrity, and availability. Refer to the Patchstack Vulnerability Advisory for the technical breakdown of the affected code path.

// No verified proof-of-concept code is publicly available for this CVE.
// See the Patchstack advisory linked above for technical details.

Detection Methods for CVE-2026-62107

Indicators of Compromise

HTTP requests to Masteriyo plugin endpoints containing serialized PHP payload markers such as O:, a:, or s: in POST bodies or query parameters
Unexpected creation or modification of PHP files under wp-content/uploads/ or the plugin directory
New or modified WordPress administrator accounts, options, or scheduled tasks (wp_options, wp_users, cron jobs) following requests to the plugin

Detection Strategies

Inspect web server access logs for POST requests to learning-management-system endpoints containing serialized object signatures
Deploy Web Application Firewall (WAF) rules that flag PHP serialization patterns in requests directed at the plugin
Correlate authenticated low-privilege user activity with subsequent file system writes on the WordPress host

Monitoring Recommendations

Enable PHP error and access logging to capture deserialization warnings and unexpected class instantiations
Monitor outbound connections from the web server for signs of reverse shells or webshell callback traffic
Track integrity of plugin files, WordPress core files, and theme directories with file integrity monitoring

How to Mitigate CVE-2026-62107

Immediate Actions Required

Update the Masteriyo LMS plugin to a version later than 3.4.0 as soon as a patched release is available
Audit WordPress user accounts and remove unnecessary low-privilege accounts that could be leveraged for exploitation
Review recent site activity, uploaded files, and administrator changes for signs of prior exploitation

Patch Information

Users should upgrade the learning-management-system plugin beyond version 3.4.0. Consult the Patchstack Vulnerability Advisory for the fixed version identifier and vendor guidance.

Workarounds

Restrict access to the WordPress site or Masteriyo endpoints using IP allow-lists until the plugin is updated
Deploy WAF signatures that block requests containing PHP serialized object markers targeting plugin routes
Temporarily deactivate the Masteriyo LMS plugin if a patched version cannot be applied immediately

bash

# Example: block requests containing PHP serialized object markers via ModSecurity
SecRule ARGS|REQUEST_BODY "@rx (?:^|[&=])O:\d+:\"" \
  "id:1092107,phase:2,deny,status:403,msg:'Possible PHP Object Injection targeting Masteriyo LMS (CVE-2026-62107)'"