CVE-2026-78175: themeum tutor lms – elearning and online course solution Deserialization of Untrusted Data

Vulnerability summary

CVE-2026-78175 is a high (CVSS 8.8) Deserialization of Untrusted Data vulnerability in themeum tutor lms – elearning and online course solution. EPSS estimates a 1.07% chance of exploitation in the next 30 days, higher than 64.5% of scored vulnerabilities. Fixed in 4.0.8.

Timeline

1. 12-09-2026
   PublishedVulnerability first disclosed.
2. 15-09-2026
   Last modifiedVulnerability information updated.

Description

The Tutor LMS – eLearning and online course solution plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 4.0.7 via the `withdraw_method_field` parameter of the `tutor_save_withdraw_account` AJAX handler. This is due to the handler lacking any capability or role check, relying solely on a nonce, while also passing attacker-supplied values through `esc_sql()`, which replaces every `%` character with a 66-byte HMAC placeholder token before the data is serialized and stored via `update_user_meta()`; when the meta is later retrieved, the placeholder is collapsed back to a single `%`, leaving serialized string length declarations 65 bytes greater than the actual content, and because array keys originate from entirely unescaped POST field names, `unserialize()` over-reads into attacker-controlled bytes, allowing injection of an arbitrary serialized object stream. This makes it possible for authenticated attackers, with subscriber-level access and above, to achieve remote code execution on the server by triggering the `GuzzleHttp\Cookie\FileCookieJar` POP chain, reachable via the `spl_autoload_register` loader in `TUTOR\RestAPI` which loads the plugin's own bundled PayPal Composer autoloader, writing attacker-controlled content to an attacker-specified filename. This has an unauthenticated pathway when user registration is enabled, which is common for students and teachers to register, and it requires the monetization feature to be enabled.

• CWE-502Deserialization of Untrusted DataThe product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.