---
id: CVE-2026-87929
title: >-
  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
summary: >-
  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 …
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-321
vendor: MaxSite
product: MaxSite CMS
affected:
  - cms >= 0.78 <= 109.6
published: '2026-09-09'
updated: '2026-09-14'
sourceUpdated: '2026-09-14T14:17:18.670'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-87929'
references:
  - url: >-
      https://github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-session-key-auth-bypass.md
    label: disclosure@vulncheck.com
  - url: 'https://github.com/maxsite/cms'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/config/config.php#L230-L254
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/maxsite/common/core/init.php#L70-L96
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/maxsite-cms-through-109.6-authentication-bypass-via-hardcoded-encryption-key
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-09-14T13:40:16.278801Z'
epss: 0.00527
epssPercentile: 0.4216
ingestedAt: '2026-09-14T15:23:07.419Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.