CVE-2026-45117 MyBB: Installer database configuration RCE
Attackers can execute arbitrary PHP code via crafted database configuration inputs during the MyBB installation process.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-45117?
CVE-2026-45117 is a critical code injection vulnerability in mybb, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
MyBB is free and open source forum software. From 1.8.13 until 1.8.40, the installer module does not properly escape user-supplied database configuration values written to the configuration file, resulting in PHP code injection and remote code execution when the installer is available. install/index.php processes the values with addcslashes(), but the $characters argument added in MyBB 1.8.13 does not include the backslash character, allowing crafted input to escape the generated PHP string. The uniquely identifying implementation details include introduced in MyBB 1.8.13. This issue is fixed in version 1.8.40.
Weakness: CWE-94
Which versions are affected by CVE-2026-45117?
How do I fix CVE-2026-45117?
No fix has been published for CVE-2026-45117 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-45117 being exploited?
There is no known exploitation of CVE-2026-45117 in the wild and no public exploit code.
Sources
Also known as GHSA-gpc4-77rp-3xqr.