CVE-2016-9403

CRITICAL

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.

Affects 2 products across 1 vendor.

CVSS 3.09.8
EPSS2.6%
Percentile85th
PatchUnknown
CVSS Vector — Plain English Remotely exploitable over the network, low complexity, no authentication required, no user interaction needed, impact contained to the vulnerable component, full confidentiality impact, full integrity impact, full availability impact.
CWE Weakness Definitions
CWE-264: Permissions, Privileges, and Access Controls

Broad class covering failures in permission enforcement. Deprecated in favor of CWE-284, CWE-862, CWE-863.

◆ AI Analysis — automated analysis, not human-reviewed

This vulnerability was disclosed in 2017. A critical vulnerability affects Mybb systems (CVE-2016-9403). No public exploit code is currently available. Isolate affected systems if patching is not feasible.

BSID: BS-2017-GLOBAL-113008-C • Model: rule-based-v1 • Confidence: MEDIUM

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Frequently Asked Questions
What is CVE-2016-9403?
This vulnerability was disclosed in 2017. A critical vulnerability affects Mybb systems (CVE-2016-9403). No public exploit code is currently available. Isolate affected systems if patching is not feasible.
What is the CVSS score for CVE-2016-9403?
CVE-2016-9403 has CVSS 9.8 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS: 2.6%.
Is CVE-2016-9403 actively exploited?
No confirmed active exploitation of CVE-2016-9403 as of 2026-09-25.
How do I remediate CVE-2016-9403?
Priority: MEDIUM. Advisory: https://blog.mybb.com/2016/03/11/mybb-1-8-7-merge-system-1-8-7-release/ PSIRT: [email protected]
What systems are affected by CVE-2016-9403?
CVE-2016-9403 affects Mybb Mybb, Merge System.
Vulnerability Details
CVE IDCVE-2016-9403
BSIDBS-2017-GLOBAL-113008-C BreachSpider Global ID
CVSS VectorCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published2017-01-31
Last Modified2026-06-17
ICS Relevance0%
Weakness (CWE)
Permissions, Privileges, and Access Controls
SourceNVD
Official 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.

Source: NIST NVD / MITRE CVE Database

Attack Vector Analysis — CITED Relevance

Vulnerability details: 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. CVSS vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Exploitation Likelihood: LOW

Affected Products
VendorProductAffected Versions
Mybb Mybb ≤ 1.8.6
Mybb Merge System ≤ 1.8.6
Remediation
View Vendor Advisory →

Remediation Priority: MEDIUM

Vendor PSIRT: [email protected]
Threat Intelligence
● Threat Intelligence Validated: October 2026 | Threat Age: 3544 Days
CISA known-exploitedNot in KEV catalog
Public ExploitNot confirmed
PoC CodeNot confirmed
AI Enrichment Record — provenance & audit hash
Modelrule-based-v1
ConfidenceMEDIUM
Enriched At2026-05-24
SHA-512 Audit Hash6098d74977509c58d5060ae6e0c5634f26646fbba4d2a3be6f4294617b5c79a16007c3d5eb048984b292995f3e6633ab056724c9efa64f1bc934335b7f36827b
Related CVEs affecting Mybb
CVE-2015-2786 10.0 Unspecified vulnerability in MyBB (aka MyBulletinBoard) before 1.8.4 has unkn... CVE-2015-8974 10.0 SQL injection vulnerability in the Group Promotions module in the admin contr... CVE-2006-0218 10.0 Multiple unspecified vulnerabilities in MyBulletinBoard (MyBB) before 1.0.2 h... CVE-2011-5133 10.0 Unspecified vulnerability in MyBB before 1.6.5 has unknown impact and attack ... CVE-2016-9402 9.8 SQL injection vulnerability in the moderation tool in MyBB (aka MyBulletinBoa...
View all Mybb CVEs →

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