CVE-2021-43281

Severity: high (CVSS 7.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-11-04 · updated 2026-06-17
Weakness: CWE-94

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.

Affected products

mybb: from 1.2.0 before 1.8.29 — fixed in 1.8.29

How to fix

Upgrade to a fixed version: mybb 1.8.29. Check the vendor advisory for mitigations.

References

https://github.com/mybb/mybb/security/advisories/GHSA-8gxx-vmr9-h39p
https://github.com/mybb/mybb/security/advisories/GHSA-8gxx-vmr9-h39p

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