How severe is CVE-2021-43281?

CVE-2021-43281 has a CVSS 3.x base score of 7.2, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-43281 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43281?

CVE-2021-43281 affects Mybb. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43281?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-43281 published?

CVE-2021-43281 was published on 2021-11-04 and last updated on 2026-06-17.

CVE-2021-43281

CVE-2021-43281 is a high-severity vulnerability in Mybb with a CVSS 3.x base score of 7.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-94.

Key facts

Severity: High (CVSS 3.x base score 7.2)
CVSS v2: 6.5
EPSS exploit prediction: 1% (67th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-94
Affected product: Mybb
Published: 2021-11-04
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-43281?: 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.
How severe is CVE-2021-43281?: CVE-2021-43281 has a CVSS 3.x base score of 7.2, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43281 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43281?: CVE-2021-43281 affects Mybb. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43281?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-43281 published?: CVE-2021-43281 was published on 2021-11-04 and last updated on 2026-06-17.

References

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

Affected products (1)

cpe:2.3:a:mybb:mybb:*:*:*:*:*:*:*:*

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