by Kastro
Paper/Archive/CVE-2026-45117

CVE-2026-45117

mybb mybb — MyBB: Installer database configuration RCE

EPSS 1%CVSS 9.8
critical.is priorityof 100
43
CVSS 9.8 (CNA)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 66.9.669 × 2013.4No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
mybb< 1.8.40–CNA

Scores by source

GitHub_M (CNA)9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refgithub.com/mybb/mybb/security/advisories/GHSA-gpc4-77rp-3xqrrefgithub.com/mybb/mybb/commit/0fe713e3b964bfc878ea65bdd9f746f585f6ebbfrefgithub.com/mybb/mybb/releases/tag/mybb_1840refmybb.com/versions/1.8.40