MyBB up to 1.8.38 path traversal

Summaryinfo

A vulnerability was found in MyBB up to 1.8.38. It has been declared as critical. Affected is an unknown function. The manipulation results in path traversal. This vulnerability was named CVE-2025-48940. The attack may be performed from remote. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in MyBB up to 1.8.38. It has been classified as critical. Affected is some unknown processing. The manipulation with an unknown input leads to a path traversal vulnerability. CWE is classifying the issue as CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2025-48940 since 05/28/2025. The exploitability is told to be easy. It is possible to launch the attack remotely. Additional levels of successful authentication are necessary for exploitation. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 06/02/2025). The MITRE ATT&CK project declares the attack technique as T1006.

Upgrading to version 1.8.39 eliminates this vulnerability.

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Productinfo

Type

• Content Management System

Name

• MyBB

Version

• 1.8.0
• 1.8.1
• 1.8.2
• 1.8.3
• 1.8.4
• 1.8.5
• 1.8.6
• 1.8.7
• 1.8.8
• 1.8.9
• 1.8.10
• 1.8.11
• 1.8.12
• 1.8.13
• 1.8.14
• 1.8.15
• 1.8.16
• 1.8.17
• 1.8.18
• 1.8.19
• 1.8.20
• 1.8.21
• 1.8.22
• 1.8.23
• 1.8.24
• 1.8.25
• 1.8.26
• 1.8.27
• 1.8.28
• 1.8.29
• 1.8.30
• 1.8.31
• 1.8.32
• 1.8.33
• 1.8.34
• 1.8.35
• 1.8.36
• 1.8.37
• 1.8.38

License

• open-source

Website

• Product: https://mybb.com/

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