CVE-2026-45117Network attack vector

Unauthenticated RCE via installer config write

Published Aug 18, 2026 · Updated Aug 18, 2026

Code injection in the installer in MyBB 1.8.13 through 1.8.39 allows remote attackers to execute arbitrary PHP code via database configuration values. In install/index.php, create_tables() writes database settings into the generated PHP configuration file with addcslashes(..., "'") so backslashes remain unescaped and crafted input can break out of the quoted string. Exploitation requires the install/ interface to remain reachable; when it does, unauthenticated network access is enough to turn a malicious setup request into server-side code execution.

CVSS severity9.8
Critical
EPSS probability0.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in the installer in MyBB 1.8.13 through 1.8.39 allows remote attackers to execute arbitrary PHP code via database configuration values. In install/index.php, create_tables() writes database settings into the generated PHP configuration file with addcslashes(..., "'") so backslashes remain unescaped and crafted input can break out of the quoted string. Exploitation requires the install/ interface to remain reachable; when it does, unauthenticated network access is enough to turn a malicious setup request into server-side code execution.

The record

CVE
CVE-2026-45117
Published
Aug 18, 2026
Updated
Aug 18, 2026
Vendor
MyBB Group
Product
MyBB
Classifications
CWE-94, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.8.40

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

MyBB Group · MyBBversion=< 1.8.40

Published CVSS scores

9.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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