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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact High

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
MaxSite MaxSite CMS unaffected
Version Status Constraints
0.78 affected ≤ 109.6

No data.

No data.

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Project Subscriptions

Vendors Products
Max-3000 Subscribe
Maxsite Cms Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-session-key-auth-bypass.md cve-icon cve-icon
https://github.com/maxsite/cms cve-icon cve-icon
https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/config/config.php#L230-L254 cve-icon cve-icon
https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/maxsite/common/core/init.php#L70-L96 cve-icon cve-icon
https://www.vulncheck.com/advisories/maxsite-cms-through-109.6-authentication-bypass-via-hardcoded-encryption-key cve-icon cve-icon
History

Wed, 09 Sep 2026 17:00:00 +0000

Type Values Removed Values Added
Description 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.
Title MaxSite CMS through 109.6 Authentication Bypass via Hardcoded Encryption Key
First Time appeared Max-3000
Max-3000 maxsite Cms
Weaknesses CWE-321
CPEs cpe:2.3:a:max-3000:maxsite_cms:*:*:*:*:*:*:*:*
Vendors & Products Max-3000
Max-3000 maxsite Cms
References
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 9.3, 'vector': '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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-09-09T16:45:00.096Z

Reserved: 2026-09-09T16:12:31.422Z

Link: CVE-2026-87929

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2026-09-09T17:17:53.840

Modified: 2026-09-09T20:14:00.420

Link: CVE-2026-87929

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-09T19:00:15Z

Weaknesses