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Vulnerability record · CVE-2021-43281 · published 4 November 2021

CVE-2021-43281: Mybb code injection vulnerability

Mybb · Mybb

MyBB before 1.8.29 allows Remote Code Injection by an admin with the "Can manage settings?" permission. The Admin CP's Settings management module does not validate setting types correctly on insertion and update, making it possible to add settings of supported type "php" with PHP code, executed on Change Settings pages.

7.2 CVSS 3.1 High EPSS 1.3% · top 29.3% CWE-94 · Code injection
7.2CVSS 3.1 base score, v2 6.5
1.3%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

MyBB before 1.8.29 allows Remote Code Injection by an admin with the "Can manage settings?" permission. The Admin CP's Settings management module does not validate setting types correctly on insertion and update, making it possible to add settings of supported type "php" with PHP code, executed on Change Settings pages.

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/mybb/mybb/security/advisories/GHSA-8gxx-vmr9-h39p PatchRelease NotesThird Party Advisory
https://github.com/mybb/mybb/security/advisories/GHSA-8gxx-vmr9-h39p PatchRelease NotesThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2011-10018Mybb code injection vulnerabilitymyBB version 1.6.4 was distributed with an unauthorized backdoor embedded in the source code. The backdoor allowed remote attackers to execute arbitr…EPSS 2.9%10.0CVE-2015-8974Mybb merge system sql injection vulnerabilitySQL injection vulnerability in the Group Promotions module in the admin control panel in MyBB (aka MyBulletinBoard) before 1.6.18 and 1.8.x before 1.…EPSS 2.1%10.0CVE-2015-2786Mybb vulnerabilityUnspecified vulnerability in MyBB (aka MyBulletinBoard) before 1.8.4 has unknown attack vectors related to "Group join request notifications sent to …EPSS 1.4%10.0CVE-2011-5133Mybb vulnerabilityUnspecified vulnerability in MyBB before 1.6.5 has unknown impact and attack vectors, related to an "unparsed user avatar in the buddy list."EPSS 1.7%10.0CVE-2006-0218Mybb vulnerabilityMultiple unspecified vulnerabilities in MyBulletinBoard (MyBB) before 1.0.2 have unspecified impact and attack vectors, related to (1) admin/moderate…EPSS 1.2%9.8CVE-2020-22612Mybb code injection vulnerabilityInstaller RCE on settings file write in MyBB before 1.8.22.EPSS 0.73%9.8CVE-2017-16780Mybb cross-site request forgery vulnerabilityThe installer in MyBB before 1.8.13 allows remote attackers to execute arbitrary code by writing to the configuration file.EPSS 5.8%9.8CVE-2016-9403Mybb merge system permissions and access controls vulnerabilitynewreply.php in MyBB (aka MyBulletinBoard) before 1.8.7 and MyBB Merge System before 1.8.7 allows remote attackers to have unspecified impact by leve…EPSS 2.6%

Source: NIST National Vulnerability Database (record CVE-2021-43281), CISA KEV, FIRST EPSS (scores of 2026-10-16). This page is refreshed as NVD updates the record.