Vulnerability in Maxsite Cms
CVE-2026-87929
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.005 (44.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 44.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
Weakness classification (CWE)
References
- github.com/maxsite/cms (product)
- github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-sess… (technical-description, exploit)
- github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/applicatio… (technical-description)
- github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/applicatio… (technical-description)
- VulnCheck Advisory: MaxSite CMS through 109.6 Authentication Bypass via Hardcoded Encryption Key (third-party-advisory)
Frequently asked questions
- What is CVE-2026-87929?
- CVE-2026-87929 is a critical-severity vulnerability in Maxsite Cms, classified under Use of Hard-coded Cryptographic Key. CVSS score: 9.8/10. Published 2026-09-09.
- How severe is CVE-2026-87929?
- Critical severity. CVSS v3 base score is 9.8 out of 10.