CVE-2025-48940
MyBB's upgrade component vulnerable to local file inclusion
In short
MyBB's upgrade component fails to validate user input, allowing attackers to read arbitrary files from the server through a path traversal flaw. This requires the installer to be unlocked and accessible, but poses a serious risk if those conditions exist.
Technical detail
Local file inclusion (CWE-22) in MyBB's upgrade component results from insufficient input validation on user-supplied parameters. Attack vector requires either an unlocked installer (missing `install/lock` file) or administrator authentication combined with access to `install/index.php`; successful exploitation allows reading arbitrary files on the server filesystem.
Summary generated and translated by AI from the official description.
MyBB is free and open source forum software. Prior to version 1.8.39, the upgrade component does not validate user input properly, which allows attackers to perform local file inclusion (LFI) via a specially crafted parameter value. In order to exploit the vulnerability, the installer must be unlocked (no `install/lock` file present) and the upgrade script must be accessible (by re-installing the forum via access to `install/index.php`; when the forum has not yet been installed; or the attacker is authenticated as a forum administrator). MyBB 1.8.39 resolves this issue.
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Affected products
mybb · mybbWant to know if your infrastructure is exposed to this?
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