Home/CVE/MyBB is free and open source forum software. Prior to version 1.8.39, the upgrade component does not validate user input
CVE

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

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.

HIGH · CVSS 7.2 EPSS 0.00505
Schedule remediation
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
▤

Affected Products & Versions

1
mybb< 1.8.39
▣

Scoring & Timeline

7.2
HIGH · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD02 Jun 2025 · 04:15 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
🔗

References & Sources

3
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/mybb/mybb/commit/6e6cfbd524d9101b51e1278ecf520479b64b0f00Patch
https://github.com/mybb/mybb/security/advisories/GHSA-q4jv-xwjx-37cpVendor Advisory
https://mybb.com/versions/1.8.39ProductRelease Notes
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