CVE-2026-39393 Post-Installation Re-entry via Cache-Dependent Install Guard Bypass in ci4ms
Unauthenticated attackers can bypass the installation guard during cache misses to overwrite configuration files and take over the application.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-39393?
CVE-2026-39393 is a high-severity authentication bypass vulnerability in ci4-cms-erp ci4ms, published on 8 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
CI4MS is a CodeIgniter 4-based CMS skeleton that delivers a production-ready, modular architecture with RBAC authorization and theme support. Prior to 0.31.4.0, the install route guard in ci4ms relies solely on a volatile cache check (cache('settings')) combined with .env file existence to block post-installation access to the setup wizard. When the database is temporarily unreachable during a cache miss (TTL expiry or admin-triggered cache clear), the guard fails open, allowing an unauthenticated attacker to overwrite the .env file with attacker-controlled database credentials, achieving full application takeover. This vulnerability is fixed in 0.31.4.0.
Weakness: CWE-306
Which versions are affected by CVE-2026-39393?
2 open source packages ship an affected version, including ci4-cms-erp/ci4ms. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
ci4-cms-erp/ci4ms Packagist | All versions | 0.31.4.0 |
ci4-cms-erp/ci4ms Packagist | All versions | 0.31.4.0 |
Products include Ci4-Cms-Erp Ci4ms.
How do I fix CVE-2026-39393?
Upgrade ci4-cms-erp/ci4ms to 0.31.4.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-39393 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39393 exists.
Other vulnerabilities in ci4-cms-erp ci4ms
- CVE-2026-34569 CI4MS: Blogs Categories Full Account Takeover for All-Roles & Privilege-Escalation via Stored DOM XSS
- CVE-2026-34571 CI4MS: Stored Cross‑Site Scripting (Stored XSS) in Backend User Management Allows Session Hijacking and Full Administrative Account Compromise
- CVE-2026-25510 CI4MS Vulnerable to Remote Code Execution (RCE) via Arbitrary File Creation and Save in File Editor
- CVE-2026-34989 CI4MS: Profile & User Management Full Account Takeover for All-Roles & Privilege-Escalation via Stored DOM XSS
- CVE-2026-34559 CI4MS: Blogs Tags Full Account Takeover for All-Roles & Privilege-Escalation via Stored DOM XSS
Sources
Also known as GHSA-8rh5-4mvx-xj7j.