Authentication Bypass in MaxSite CMS by Hardcoded Encryption Key
CVE-2026-87929

9.3CRITICAL

Key Information:

Vendor

Maxsite

Status
Maxsite Cms
Vendor
CVE Published:
9 September 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-87929?

MaxSite CMS versions up to 109.6 contain a significant vulnerability where a hardcoded session encryption key is embedded in 'application/config/config.php'. This constant key is never altered during installation, rendering the system vulnerable to authentication bypass by unauthenticated attackers. Malicious users can forge administrator session cookies by generating an HMAC-SHA1 with the known key, which allows them to circumvent security measures in the is_login() and mso_check_allow() functions.

Affected Version(s)

MaxSite CMS 0.78 <= 109.6

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-87929 - Proof of Concept

References

https://github.com/maxsite/cms
product
https://github.com/EviL0rd/maxsite-cve4/blob/main/2026.09...
exploittechnical-description
https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25db...
technical-description

CVSS V4

Score:
9.3
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

EVIL0RD
.