What is CVE-2026-87930?

CVE-2026-87930 is a high-severity vulnerability in Maxsite Cms, classified under Deserialization of Untrusted Data. CVSS score: 8.1/10. Published 2026-09-09.

How severe is CVE-2026-87930?

High severity. CVSS v3 base score is 8.1 out of 10.

Is CVE-2026-87930 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Deserialization in Maxsite Cms

CVE-2026-87930

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.

Vulnerability class: Insecure Deserialization

Published 2026-09-09 · last modified 2026-09-09.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.006 (48.7th percentile), scored 2026-10-26.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 48.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000

Affected products

Maxsite Cms

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

Public proof-of-concept exploits

winrarzipsexploit/CVE-2026-87930

References

github.com/maxsite/cms (product)
github.com/EviL0rd/maxsite-cve6/blob/main/2026.09.08-maxsite-cms-unsafe-unseria… (technical-description, exploit)
github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/system/lib… (technical-description)
github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/system/lib… (technical-description)
github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-sess… (technical-description)
github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/applicatio… (technical-description)
VulnCheck Advisory: MaxSite CMS through 109.6 PHP Object Injection via ci_session (third-party-advisory)

Frequently asked questions

What is CVE-2026-87930?: CVE-2026-87930 is a high-severity vulnerability in Maxsite Cms, classified under Deserialization of Untrusted Data. CVSS score: 8.1/10. Published 2026-09-09.
How severe is CVE-2026-87930?: High severity. CVSS v3 base score is 8.1 out of 10.
Is CVE-2026-87930 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.