CVE-2025-48940: mybb Path Traversal — Fix

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.

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CVSS v3.1 Score

7.2

HIGH

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-22 Path Traversal

Affected Products

Vendor	Product	Versions
mybb	mybb	< 1.8.39

References

Advisories & Patches

https://github.com/mybb/mybb/commit/6e6cfbd524d9101b51e1278ecf520479b64b0f00 https://github.com/mybb/mybb/security/advisories/GHSA-q4jv-xwjx-37cp

Other References

https://mybb.com/versions/1.8.39

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 7.2 (HIGH).

How severe is CVE-2025-48940? +

CVE-2025-48940 has a CVSS v3.1 score of 7.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-48940? +

CVE-2025-48940 affects products from mybb, specifically: mybb. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-48940? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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