Vulnerability · Published Sep 9, 2026 · Assigned by VulnCheck
CVE-2026-87930MaxSite CMS through 109.6 PHP Object Injection via ci_session
High 8.1
In plain English
A high-severity unsafe deserialization in MaxSite CMS from MaxSite. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 49% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.
Official description
MaxSite CMS through 109.6 passes the ci_session cookie to unserialize() without class restrictions, allowing unauthenticated attackers to inject PHP objects. Attackers can forge valid session cookies using the hardcoded encryption key to trigger magic methods and corrupt application state or achieve code execution if gadget classes exist.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| MaxSite | MaxSite CMS | 0.78 – through 109.6 |
Weakness: CWE-502 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://github.com/maxsite/cms product
- https://github.com/EviL0rd/maxsite-cve6/blob/main/2026.09.08-maxsite-cms-unsafe-unserialize-object-injection.md exploit, technical-description
- https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/system/libraries/Session.php#L670-L680 technical-description
- https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/system/libraries/Session.php#L740-L742 technical-description
- https://github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-session-key-auth-bypass.md technical-description
- https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/config/config.php#L230-L254 technical-description
- VulnCheck Advisory: MaxSite CMS through 109.6 PHP Object Injection via ci_session third-party-advisory