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CVE-2026-45123— MyBB: IPv6 SSRF

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之前版本存在服务端请求伪造漏洞，该漏洞源于远程请求功能未正确处理IPv6地址，导致服务端请求伪造漏洞。

CVSS 4.3 · Medium EPSS 0.27% · P19

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-2026-45123

Vulnerability Information
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Vulnerability Title
MyBB: IPv6 SSRF
Source: CVE Program / CVE List V5
Vulnerability Description
MyBB is free and open source forum software. Prior to 1.8.40, the remote requests feature does not correctly handle IPv6 addresses, resulting in a server-side request forgery vulnerability. The default disallowed remote hosts list does not include IPv6 addresses. Verification in fetch_remote_file() fails open when get_ip_by_hostname() returns no result because that function does not return IPv6 results, allowing a crafted remote target to bypass the host restriction. The uniquely identifying implementation details include fail-open verification, and inc/functions.php. 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:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
MyBB 服务端请求伪造漏洞
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之前版本存在服务端请求伪造漏洞，该漏洞源于远程请求功能未正确处理IPv6地址，导致服务端请求伪造漏洞。
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-2026-45123

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III. Intelligence Information for CVE-2026-45123

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Patches & Fixes for CVE-2026-45123 (2)

Vendor Advisories for CVE-2026-45123 (1)

Vendor Pages for CVE-2026-45123 (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-2026-45115 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-2026-45122 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-918

V. Comments for CVE-2026-45123

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