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CVE-2026-45125— MyBB: Email User CRLF injection

Quick assessment

Affected
mybb mybb
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
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之前版本存在输入验证错误漏洞，该漏洞源于Email User控制器未正确清理发件人名称，可能导致邮件头注入，允许通过CRLF序列注入任意标头。

CVSS 5.3 · Medium EPSS 0.30% · P23

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
mybb mybb < 1.8.40 affected
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I. Basic Information for CVE-2026-45125

Vulnerability Information
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Vulnerability Title
MyBB: Email User CRLF injection
Source: CVE Program / CVE List V5
Vulnerability Description
MyBB is free and open source forum software. Prior to 1.8.40, the Email User controller does not sanitize sender names correctly, resulting in mail header injection. member.php?action=do_emailuser accepts the fromname HTTP parameter for guests or the stored username for authenticated users when the cansendemail group permission is enabled. When mail_handler is set to the default PHP mail value, the sender name is used without sanitization in Return-Path and Reply-To headers, allowing arbitrary headers to be injected with CRLF sequences. 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:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对CRLF序列的转义处理不恰当(CRLF注入)
Source: CVE Program / CVE List V5
Vulnerability Title
MyBB 输入验证错误漏洞
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之前版本存在输入验证错误漏洞，该漏洞源于Email User控制器未正确清理发件人名称，可能导致邮件头注入，允许通过CRLF序列注入任意标头。
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-2026-45125

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III. Intelligence Information for CVE-2026-45125

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Patches & Fixes for CVE-2026-45125 (2)

Vendor Advisories for CVE-2026-45125 (1)

Vendor Pages for CVE-2026-45125 (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-2026-45115 8.7 HIGH MyBB: Buddy/ignore list username 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-2026-45119 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-93

V. Comments for CVE-2026-45125

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