Path Traversal in Mybb
CVE-2025-48940
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.
Vulnerability class: Path Traversal (Directory Traversal)
EPSS: 0.005 (38.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Mybb — versions < 1.8.39
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2025-48940?
- CVE-2025-48940 is a high-severity vulnerability in Mybb, classified under Path Traversal. CVSS score: 7.2/10. Published 2025-06-02.
- How severe is CVE-2025-48940?
- High severity. CVSS v3 base score is 7.2 out of 10.