How severe is CVE-2016-9403?

CVE-2016-9403 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2016-9403 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-9403?

CVE-2016-9403 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-2016-9403?

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

When was CVE-2016-9403 published?

CVE-2016-9403 was published on 2017-01-31 and last updated on 2026-06-17.

CVE-2016-9403

CVE-2016-9403 is a critical-severity vulnerability in Mybb Merge System with a CVSS 3.x base score of 9.8. 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-264.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (83rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-264
Affected product: Mybb Merge System
Published: 2017-01-31
Last modified: 2026-06-17

Description

newreply.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 leveraging a missing permission check.

Frequently asked questions

What is CVE-2016-9403?: newreply.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 leveraging a missing permission check.
How severe is CVE-2016-9403?: CVE-2016-9403 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2016-9403 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-9403?: CVE-2016-9403 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-2016-9403?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2016-9403 published?: CVE-2016-9403 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:*:*:*:*:*:*:*:*

More vulnerabilities in Mybb Merge System

CVE-2015-8974 — Critical (CVSS 10.0): SQL injection vulnerability in the Group Promotions module in the admin control panel in MyBB (aka MyBulletinBoard)…
CVE-2016-9420 — Critical (CVSS 9.8): MyBB (aka MyBulletinBoard) before 1.8.8 and MyBB Merge System before 1.8.8 allow remote attackers to have unspecified…
CVE-2016-9416 — Critical (CVSS 9.8): SQL injection vulnerability in the users data handler in MyBB (aka MyBulletinBoard) before 1.8.8 and MyBB Merge System…
CVE-2016-9412 — Critical (CVSS 9.8): MyBB (aka MyBulletinBoard) before 1.8.7 and MyBB Merge System before 1.8.7 allow attackers to have unspecified impact…
CVE-2016-9402 — Critical (CVSS 9.8): SQL injection vulnerability in the moderation tool in MyBB (aka MyBulletinBoard) before 1.8.7 and MyBB Merge System…
CVE-2015-8973 — High (CVSS 8.3): xmlhttp.php in MyBB (aka MyBulletinBoard) before 1.6.18 and 1.8.x before 1.8.6 and MyBB Merge System before 1.8.6…

All CVEs affecting Mybb Merge System →

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