MyBB up to 1.8.39 UTF-8 Conversion system_health.php table privileges management

Summaryinfo

A vulnerability was found in MyBB up to 1.8.39. It has been declared as problematic. This impacts an unknown function of the file admin/modules/tools/system_health.php of the component UTF-8 Conversion. Such manipulation of the argument table leads to privileges management. This vulnerability is documented as CVE-2026-45119. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in MyBB up to 1.8.39. It has been rated as problematic. Affected by this issue is some unknown processing of the file admin/modules/tools/system_health.php of the component UTF-8 Conversion. The manipulation of the argument table with an unknown input leads to a privileges management vulnerability. Using CWE to declare the problem leads to CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. Impacted is integrity, and availability. CVE summarizes:

MyBB is free and open source forum software. Prior to 1.8.40, the Admin CP UTF-8 Conversion module does not validate certain requests correctly, allowing same-site attackers to alter table encoding and deny service with a specially crafted URL. The do=all control flow in admin/modules/tools/system_health.php performs ALTER TABLE operations, column rewrite phases, and fulltext index rebuilds on GET requests for the database table named by the table parameter without request verification. The uniquely identifying implementation details include GET requests without request verification. This issue is fixed in version 1.8.40.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-45119 since 05/08/2026. The exploitation is known to be easy. The attack may be launched remotely. The exploitation needs additional levels of successful authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 08/18/2026). The MITRE ATT&CK project declares the attack technique as T1068.

By approaching the search of inurl:admin/modules/tools/system_health.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 1.8.40 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

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
• 1.8.39

License

• open-source

Website

• Product: https://mybb.com/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Once again VulDB remains the best source for vulnerability data.

Discussion