CVE-2026-45117 | BDVDB-2026-360829 Detail

mybbmybb

Description#

MyBB is free and open source forum software. From 1.8.13 until 1.8.40, the installer module does not properly escape user-supplied database configuration values written to the configuration file, resulting in PHP code injection and remote code execution when the installer is available. install/index.php processes the values with addcslashes(), but the $characters argument added in MyBB 1.8.13 does not include the backslash character, allowing crafted input to escape the generated PHP string. The uniquely identifying implementation details include introduced in MyBB 1.8.13. This issue is fixed in version 1.8.40.

Impact#

Per CVSS v3.1: confidentiality impact high, integrity impact high, availability impact high. Attack vector: network.

Weaknesses#

CWE-94 Improper Control of Generation of Code ('Code Injection')

References#

Exploit#

No public exploit known

History#

Version 12026-08-18Record published in the CVE List.

Published

Published: 2026-08-18
Last modified: 2026-08-18

Vendor information

Vendor: mybb
Product: mybb

All mybb vulnerabilities

Score

9.8 Critical

EPSS

1.1%, Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 67.1.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Code Injection

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
< 1.8.40
Fixed
Not stated

Scoring System

CVSS v4.0

Not available

CVSS v3.1

9.8 Critical

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Metric breakdown
Attack Vector	Network
Attack Complexity	Low
Privileges Required	None
User Interaction	None
Scope	Unchanged
Confidentiality	High
Integrity	High
Availability	High

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).