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CVE-2026-45116

MyBB: Profile field type confusion XSS

Published: Aug 18, 2026Updated: Aug 18, 2026 Sources: CVE List NVDCWE-79
8.7HIGH
NVD MITRE
EPSS Score
0.3%
Top 77.1%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

Description

MyBB is free and open source forum software. Prior to 1.8.40, the user datahandler does not properly validate checkbox and multiselect profile field types, resulting in stored JavaScript code injection. UserDataHandler::verify_profile_fields() only performs the specialized validation when is_array($profile_fields[$field]) is true. A non-array profile_fields[fidX] value instead of the expected profile_fields[fidX][] shape falls through to generic text handling and is stored without verification. The affected value is then rendered directly by member.php and inc/functions_post.php rather than processed by the MyCode parser. The uniquely identifying implementation details include inc/datahandlers/user.php. This issue is fixed in version 1.8.40.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:RS:CC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:RUser Interaction
Required
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-79

Affected Products

mybb
oss-projectaka mybb forums
mybb
Web & CMS Plugins

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Execution
Initial Access
View detailed technique mapping

References

https://github.com/mybb/mybb/commit/c32f0c22baab704a68b8d58fcdd2f26fadbbe19b
github.com
https://github.com/mybb/mybb/releases/tag/mybb_1840
github.com
https://github.com/mybb/mybb/security/advisories/GHSA-4p6g-p3qh-559v
github.com
and 1 more references View all →

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