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CVE-2026-45115— MyBB: Buddy/ignore list username XSS

Quick assessment

Affected
mybb mybb
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

MyBB是MyBB组织开源的一套用PHP和MySQL开发的免费且基于Web的论坛软件。该软件具有简单易用、支持多国语言、可扩展等特点。 MyBB 1.8.40之前版本存在跨站脚本漏洞，该漏洞源于Buddy/Ignore组件未正确清理用户名，可能导致特制用户名触发JavaScript代码注入。

CVSS 8.7 · High EPSS 0.29% · P21

Possible ATT&CK Techniques 1 AI

T1059.007 · JavaScript

Affected Version Matrix 1

VendorProduct Version RangeStatus
mybb mybb < 1.8.40 affected
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I. Basic Information for CVE-2026-45115

Vulnerability Information
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Vulnerability Title
MyBB: Buddy/ignore list username XSS
Source: CVE Program / CVE List V5
Vulnerability Description
MyBB is free and open source forum software. Prior to 1.8.40, the Buddy/Ignore component does not sanitize usernames correctly, allowing attackers to perform JavaScript code injection through a specially crafted username. The User CP Buddy/Ignore list and the Select Buddies list in Private Messages pass usernames through htmlspecialchars_uni(), which may leave single quotes unescaped. The payload is triggered when a victim chooses Yes in Please Confirm while removing the username in usercp.php, or selects the username through the onclick handler in the xmlhttp.php Select Buddies popup. The uniquely identifying implementation details include Private Messages Select Buddies list, and unescaped single quotes. This issue is fixed in version 1.8.40.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
MyBB 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
MyBB是MyBB组织开源的一套用PHP和MySQL开发的免费且基于Web的论坛软件。该软件具有简单易用、支持多国语言、可扩展等特点。 MyBB 1.8.40之前版本存在跨站脚本漏洞，该漏洞源于Buddy/Ignore组件未正确清理用户名，可能导致特制用户名触发JavaScript代码注入。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mybb mybb < 1.8.40 -

II. Public POCs for CVE-2026-45115

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 7941 chars
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III. Intelligence Information for CVE-2026-45115

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Patches & Fixes for CVE-2026-45115 (1)

Vendor Advisories for CVE-2026-45115 (1)

Vendor Pages for CVE-2026-45115 (1)

Same Patch Batch · mybb · 2026-08-18 · 18 CVEs total

CVE-2026-45117 9.8 CRITICAL MyBB: Installer database configuration RCE
CVE-2026-45118 9.3 CRITICAL MyBB: Contact page reflected XSS
CVE-2026-45116 8.7 HIGH MyBB: Profile field type confusion XSS
CVE-2026-45120 5.4 MEDIUM MyBB: Insufficient authorization for private calendar events
CVE-2026-46482 5.3 MEDIUM MyBB: Security Question insufficient validation
CVE-2026-45125 5.3 MEDIUM MyBB: Email User CRLF injection
CVE-2026-45734 5.3 MEDIUM MyBB: Default CAPTCHA missing invalidation
CVE-2026-45119 4.6 MEDIUM MyBB: ACP UTF-8 Conversion CSRF
CVE-2026-45129 4.6 MEDIUM MyBB: ACP Recovery Codes CSRF
CVE-2026-45123 4.3 MEDIUM MyBB: IPv6 SSRF
CVE-2026-47245 4.3 MEDIUM MyBB: Buddy list corruption
CVE-2026-45124 4.3 MEDIUM MyBB: Mod CP report resolution missing authorization
CVE-2026-45122 4.3 MEDIUM MyBB: Insufficient permission check for calendar event move
CVE-2026-45121 4.3 MEDIUM MyBB: Insufficient permission check for calendar select
CVE-2026-45127 3.5 LOW MyBB: ACP Mass Mail draft resend CSRF
CVE-2026-45126 3.5 LOW MyBB: ACP Questions state CSRF
CVE-2026-45128 3.5 LOW MyBB: ACP Users View Manager default CSRF

IV. Related Vulnerabilities

Same product: mybb
Same vendor: mybb
Same weakness: CWE-79

V. Comments for CVE-2026-45115

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