JavaScript Code Injection Vulnerability in MyBB Forum Software
CVE-2026-45115

8.7HIGH

Key Information:

Vendor

Mybb

Status
Mybb
Vendor
CVE Published:
18 August 2026

What is CVE-2026-45115?

MyBB forum software versions prior to 1.8.40 have a vulnerability in the Buddy/Ignore component that does not properly sanitize usernames, enabling attackers to execute JavaScript code injections. This issue arises when usernames containing unescaped single quotes are processed in usercp.php or accessed via the Select Buddies list in Private Messages. Attackers can exploit this vulnerability by tricking a victim into interacting with the manipulated username, leading to potential security breaches. The vulnerability was addressed in version 1.8.40.

Affected Version(s)

mybb < 1.8.40

References

https://github.com/mybb/mybb/security/advisories/GHSA-p76...
x_refsource_CONFIRM
https://github.com/mybb/mybb/releases/tag/mybb_1840
x_refsource_MISC
https://mybb.com/versions/1.8.40
x_refsource_MISC

CVSS V3.1

Score:
8.7
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
Required
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.