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CVE-2026-45118— MyBB: Contact page reflected 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Contact模块未正确验证重定向URL或协议，可能导致开放重定向和反射型JavaScript代码注入。

CVSS 9.3 · Critical EPSS 0.38% · P32

Affected Version Matrix 1

VendorProduct Version RangeStatus
mybb mybb < 1.8.40 affected
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I. Basic Information for CVE-2026-45118

Vulnerability Information
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Vulnerability Title
MyBB: Contact page reflected XSS
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
Web页面属性中脚本转义处理不恰当
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Contact模块未正确验证重定向URL或协议，可能导致开放重定向和反射型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-2026-45118

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Qwen3.6-35B-A3B · 10432 chars
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
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III. Intelligence Information for CVE-2026-45118

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Patches & Fixes for CVE-2026-45118 (1)

Vendor Advisories for CVE-2026-45118 (1)

Vendor Pages for CVE-2026-45118 (1)

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

CVE-2026-45117 9.8 CRITICAL MyBB: Installer database configuration RCE
CVE-2026-45115 8.7 HIGH MyBB: Buddy/ignore list username 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-2026-45734 5.3 MEDIUM MyBB: Default CAPTCHA missing invalidation
CVE-2026-45125 5.3 MEDIUM MyBB: Email User CRLF injection
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-2026-45122 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-2026-45124 4.3 MEDIUM MyBB: Mod CP report resolution missing authorization
CVE-2026-47245 4.3 MEDIUM MyBB: Buddy list corruption
CVE-2026-45126 3.5 LOW MyBB: ACP Questions state CSRF
CVE-2026-45128 3.5 LOW MyBB: ACP Users View Manager default CSRF
CVE-2026-45127 3.5 LOW MyBB: ACP Mass Mail draft resend CSRF

IV. Related Vulnerabilities

Same product: mybb
Same vendor: mybb
Same weakness: CWE-83

V. Comments for CVE-2026-45118

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