How severe is CVE-2016-9421?

CVE-2016-9421 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2016-9421 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-9421?

CVE-2016-9421 primarily affects Mybb Merge System. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2016-9421?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2016-9421 published?

CVE-2016-9421 was published on 2017-01-31 and last updated on 2026-06-17.

CVE-2016-9421

CVE-2016-9421 is a medium-severity vulnerability in Mybb Merge System with a CVSS 3.x base score of 6.1. 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-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 4.3
EPSS exploit prediction: 1% (66th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Mybb Merge System
Published: 2017-01-31
Last modified: 2026-06-17

Description

Cross-site scripting (XSS) vulnerability in the Users module in the Admin control panel in MyBB (aka MyBulletinBoard) before 1.8.8 and MyBB Merge System before 1.8.8 might allow remote attackers to inject arbitrary web script or HTML via unspecified vectors.

Frequently asked questions

What is CVE-2016-9421?: Cross-site scripting (XSS) vulnerability in the Users module in the Admin control panel in MyBB (aka MyBulletinBoard) before 1.8.8 and MyBB Merge System before 1.8.8 might allow remote attackers to inject arbitrary web script or HTML via unspecified vectors.
How severe is CVE-2016-9421?: CVE-2016-9421 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2016-9421 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-9421?: CVE-2016-9421 primarily affects Mybb Merge System. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-9421?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2016-9421 published?: CVE-2016-9421 was published on 2017-01-31 and last updated on 2026-06-17.

References

Affected products (2)

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

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