Vulnerability record · CVE-2026-87929 · published 9 September 2026

CVE-2026-87929: MaxSite CMS through 109.6 ships with a hardcoded session encryption key in application/config/config.php that …

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.

9.3 CVSS 4.0 Critical EPSS 0.53% · top 57.6% CWE-321 · CWE-321 Deferred

9.3CVSS 4.0 base score

0.53%EPSS exploitation probability, 30 days

NoNot in CISA KEV

0Affected product versions listed by NVD

5References

14 Sep 2026Last modified by NVD

Description

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

Link	Tags
https://github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-session-key-auth-bypass.md
https://github.com/maxsite/cms
https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/config/config.php#L230-L254
https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/maxsite/common/core/init.php#L7
https://www.vulncheck.com/advisories/maxsite-cms-through-109.6-authentication-bypass-via-hardcoded-encryption-key

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Source: NIST National Vulnerability Database (record CVE-2026-87929), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.