by Kastro
Paper/Archive/CVE-2026-87929

CVE-2026-87929

MaxSite MaxSite CMS — MaxSite CMS through 109.6 Authentication Bypass via Hardcoded Encryption Key

EPSS 0.5%public exploitCVSS 9.8
critical.is priorityof 100
48
CVSS 9.8 (CNA)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 44.7.447 × 208.9Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
MaxSite CMS0.78 – 109.6–CNA

Scores by source

VulnCheck (CNA)9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
VulnCheck (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CISA ADPSSVCExploitation: poc · Automatable: yes · Technical impact: total

References

refgithub.com/maxsite/cmsexploitgithub.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-session-key-auth-bypass.mdwriteupgithub.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/config/config.php#L230-L254writeupgithub.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/maxsite/common/core/init.php#L70-L96writeupvulncheck.com/advisories/maxsite-cms-through-109.6-authentication-bypass-via-hardcoded-encryption-key