CVE-2026-87929CWE-321

CVE-2026-87929

Critical · published September 9, 2026

CVSS v3.1
9.8
EPSS
1%
Percentile
43.8
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
9.8 · CRITICAL
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
9.3 · 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
EPSS
0.00527 · 43.8th percentile
Weakness
CWE-321 · Use of Hard-coded Cryptographic Key
Published
2026-09-09T21:17Z
References (5)
https://github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-session-key-auth-bypass.md · [email protected]https://github.com/maxsite/cms · [email protected]https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/config/config.php#L230-L254 · [email protected]https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/maxsite/common/core/init.php#L70-L96 · [email protected]https://www.vulncheck.com/advisories/maxsite-cms-through-109.6-authentication-bypass-via-hardcoded-encryption-key · [email protected]
EPSS history
Timeline
  • 11 SEP 03:19Z
    EPSS moved — → 0%
    epss
  • 09 SEP 16:45Z
    MaxSite CMS through 109.6 Authentication Bypass via Hardcoded Encryption Key
    cvelistv5