CVE-2026-8365: creativethemeshq blocksy Deserialization of Untrusted Data

Vulnerability summary

CVE-2026-8365 is a high (CVSS 8.8) Deserialization of Untrusted Data vulnerability in creativethemeshq blocksy. EPSS estimates a 1.60% chance of exploitation in the next 30 days, higher than 75.4% of scored vulnerabilities. Fixed in 2.1.42.

Timeline

1. 09-06-2026
   PublishedVulnerability first disclosed.
2. 09-06-2026
   Last modifiedVulnerability information updated.

Description

The Blocksy theme for WordPress is vulnerable to PHP Object Injection leading to Remote Code Execution via the 'blocksy_meta' REST API field and the V200 database migration in versions up to and including 2.1.35. This is due to insufficient input sanitization in the blocksy_sanitize_post_meta_options() function, which only blocks values containing '<' or '>' and does not prevent serialized PHP object strings from being stored in post meta, combined with the SearchReplacer::run_recursively() function unconditionally deserializing all string values via @unserialize() during migration without restricting allowed classes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject a serialized Blocksy\RaiiPattern object into post meta that, when the V200 migration runs on an upgraded site, is deserialized and triggers RaiiPattern::__destruct(), which executes arbitrary PHP callables via call_user_func().

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