Vulnerabilities
Vulnerable Software
Mybb:  >> Mybb  Security Vulnerabilities
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.
CVSS Score
7.2
EPSS Score
0.001
Published
2025-06-02
MyBB is free and open source forum software. Prior to version 1.8.39, the search component does not validate permissions correctly, which allows attackers to determine the existence of hidden (draft, unapproved, or soft-deleted) threads containing specified text in the title. The visibility state (`mybb_threads.visible` integer column) of threads is not validated in internal search queries, whose result is used to output a general success or failure of the search. While MyBB validates permissions when displaying the final search results, a search operation that internally produces at least one result outputs a redirect response (as a HTTP redirect, or a success message page with delayed redirect, depending on configuration). On the other hand, a search operation that internally produces no results outputs a corresponding message in the response without a redirect. This allows a user to determine whether threads matching title search parameters exist, including draft threads (`visible` with a value of `-2`), soft-deleted threads (`visible` with a value of `-1`), and unapproved threads (`visible` with a value of `0`); in addition to displaying generally visible threads (`visible` with a value of `1`). This vulnerability does not affect other layers of permissions. In order to exploit the vulnerability, the user must have access to the search functionality, and general access to forums containing the thread(s). The vulnerability does not expose the message content of posts. MyBB 1.8.39 resolves this issue.
CVSS Score
5.3
EPSS Score
0.0
Published
2025-06-02
An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Import a Theme function. NOTE: the Supplier disputes this because of the allowed actions of Board administrators and because of SSRF mitigation.
CVSS Score
7.6
EPSS Score
0.002
Published
2025-04-17
An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Change Avatar function. NOTE: the Supplier disputes this because of the allowed actions of Board administrators and because of SSRF mitigation.
CVSS Score
7.6
EPSS Score
0.002
Published
2025-04-17
An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Mail function. NOTE: the Supplier disputes this because of the allowed actions of Board administrators and because of SSRF mitigation.
CVSS Score
7.6
EPSS Score
0.002
Published
2025-04-17
An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Add Mycode function. NOTE: the Supplier disputes this because of the allowed actions of Board administrators and because of SSRF mitigation.
CVSS Score
7.6
EPSS Score
0.002
Published
2025-04-17
MyBB is a free and open source forum software. The backup management module of the Admin CP may accept `.htaccess` as the name of the backup file to be deleted, which may expose the stored backup files over HTTP on Apache servers. MyBB 1.8.38 resolves this issue. Users are advised to upgrade. There are no known workarounds for this vulnerability
CVSS Score
4.7
EPSS Score
0.001
Published
2024-05-01
MyBB is a free and open source forum software. The default list of disallowed remote hosts does not contain the `127.0.0.0/8` block, which may result in a Server-Side Request Forgery (SSRF) vulnerability. The Configuration File's _Disallowed Remote Addresses_ list (`$config['disallowed_remote_addresses']`) contains the address `127.0.0.1`, but does not include the complete block `127.0.0.0/8`. MyBB 1.8.38 resolves this issue in default installations. Administrators of installed boards should update the existing configuration (`inc/config.php`) to include all addresses blocked by default. Additionally, users are advised to verify that it includes any other IPv4 addresses resolving to the server and other internal resources. Users unable to upgrade may manually add 127.0.0.0/8' to their disallowed address list.
CVSS Score
5.0
EPSS Score
0.001
Published
2024-05-01
Cross Site Scripting vulnerability in Mybb Mybb Forums v.1.8.33 allows a local attacker to execute arbitrary code via the theme Name parameter in the theme management component.
CVSS Score
5.4
EPSS Score
0.001
Published
2023-11-06
MyBB is a free and open source forum software. Custom MyCode (BBCode) for the visual editor (_SCEditor_) doesn't escape input properly when rendering HTML, resulting in a DOM-based XSS vulnerability. This weakness can be exploited by pointing a victim to a page where the visual editor is active (e.g. as a post or Private Message) and operates on a maliciously crafted MyCode message. This may occur on pages where message content is pre-filled using a GET/POST parameter, or on reply pages where a previously saved malicious message is quoted. The impact is be mitigated when: 1. the visual editor is disabled globally (_Admin CP → Configuration → Settings → Clickable Smilies and BB Code: [Clickable MyCode Editor](https://github.com/mybb/mybb/blob/mybb_1836/install/resources/settings.xml#L2087-L2094)_ is set to _Off_), or 2. the visual editor is disabled for individual user accounts (_User CP → Your Profile → Edit Options_: _Show the MyCode formatting options on the posting pages_ checkbox is not checked). MyBB 1.8.37 resolves this issue with the commit `6dcaf0b4d`. Users are advised to upgrade. Users unable to upgrade may mitigate the impact without upgrading MyBB by changing the following setting (_Admin CP → Configuration → Settings_): - _Clickable Smilies and BB Code → [Clickable MyCode Editor](https://github.com/mybb/mybb/blob/mybb_1836/install/resources/settings.xml#L2087-L2094)_: _Off_. Similarly, individual MyBB forum users are able to disable the visual editor by diabling the account option (_User CP → Your Profile → Edit Options_) _Show the MyCode formatting options on the posting pages_.
CVSS Score
7.5
EPSS Score
0.007
Published
2023-11-06


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