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CVE-2026-45118

MyBB: Contact page reflected XSS

Published: Aug 18, 2026Updated: Aug 18, 2026 Sources: CVE List NVDCWE-83
9.3CRITICAL
NVD MITRE
EPSS Score
0.4%
Top 68.3%
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 Contact module does not validate a redirect URL or protocol correctly, resulting in an open redirect and reflected JavaScript code injection. contact.php accepts the redirect target from the from HTTP parameter in $mybb->input['from'] or the Referer HTTP header in $_SERVER['HTTP_REFERER'] and passes it to redirect() without sufficient verification. A javascript: URI becomes the target of the `Click here if you don't want to wait any longer` link because $force_redirect is true, allowing script execution when a victim selects the link. This issue is fixed in version 1.8.40.

No summary for this CVE yet.

CVSS Vector Breakdown

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

CWE-83

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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References

https://github.com/mybb/mybb/releases/tag/mybb_1840
github.com
https://github.com/mybb/mybb/security/advisories/GHSA-wf92-5q5h-qr53
github.com
https://mybb.com/versions/1.8.40
mybb.com

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