CVE-2026-87929: Maxsite CMS

Critical severity, CVSS 9.8. EPSS: 0.5% chance of exploitation in the next 30 days.

MaxSite CMS through 109.6 ships with a hardcoded session encryption key in application/config/config.php that is never changed during installation, allowing unauthenticated attackers to forge administrator session cookies. Attackers can mint a malicious ci_session cookie with administrator privileges by computing an HMAC-SHA1 using the publicly known encryption key, bypassing authentication checks in is_login() and mso_check_allow() functions.

Affected products

• Maxsite Maxsite CMS: from 0.78, up to and including 109.6

Published 2026-09-09. Last modified 2026-09-14.