# CVE-2026-87929: MaxSite CMS hardcoded session encryption key auth bypass

Source: https://junglewise.ai/threats/cve-2026-87929-maxsite-cms-hardcoded-session-encryption-key-auth-bypass  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-09. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-87929 · Severity: critical · CVSS 9.8 · Published 2026-09-09

MaxSite CMS is a content management system for websites and blogs. An attacker can forge administrator session cookies without credentials because the application uses a hardcoded, publicly known encryption key that is never changed during installation. This allows an unauthenticated attacker to gain full administrative access to any MaxSite CMS instance.

## Quick answers

**Is CVE-2026-87929 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-87929 being exploited in the wild.

**How severe is CVE-2026-87929?** Critical severity, with a CVSS score of 9.8, published 9 September 2026.

**Which products and versions are affected?** MaxSite CMS through 109.6.

**Is there a fix for CVE-2026-87929?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-87929 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-87929?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability combines three defects: (1) the session encryption key is hardcoded as 'encryption key' in application/config/config.php and never changed by the installer, (2) sessions are stored in ci_session cookies as PHP-serialized data signed with only HMAC-SHA1 using the public key, allowing attackers to forge cookies with arbitrary contents like userlogged=1 and users_groups_id=1, and (3) the database re-validation in init.php passes malformed ciphertext (which decrypts to boolean false) directly to database queries, causing MySQL to match the administrator row. An unauthenticated network attacker can forge a valid administrator session cookie and access the admin panel without any credentials. Versions 109.6 and earlier using CodeIgniter 2.x session handling are affected.

## Affected products

- MaxSite CMS through 109.6

## Timeline

- 2026-09-09: disclosed
- 2026-09-08: other: Advisory published on GitHub

## References

- [https://github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-session-key-auth-bypass.md](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)